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PERLFUNC(1)	       Perl Programmers Reference Guide		   PERLFUNC(1)

NAME
       perlfunc - Perl builtin functions

DESCRIPTION
       The functions in this section can serve as terms in an expression.
       They fall into two major categories: list operators and named unary
       operators.  These differ in their precedence relationship with a
       following comma.	 (See the precedence table in perlop.)	List operators
       take more than one argument, while unary operators can never take more
       than one argument.  Thus, a comma terminates the argument of a unary
       operator, but merely separates the arguments of a list operator.	 A
       unary operator generally provides a scalar context to its argument,
       while a list operator may provide either scalar or list contexts for
       its arguments.  If it does both, the scalar arguments will be first,
       and the list argument will follow.  (Note that there can ever be only
       one such list argument.)	 For instance, splice() has three scalar
       arguments followed by a list, whereas gethostbyname() has four scalar
       arguments.

       In the syntax descriptions that follow, list operators that expect a
       list (and provide list context for the elements of the list) are shown
       with LIST as an argument.  Such a list may consist of any combination
       of scalar arguments or list values; the list values will be included in
       the list as if each individual element were interpolated at that point
       in the list, forming a longer single-dimensional list value.  Commas
       should separate elements of the LIST.

       Any function in the list below may be used either with or without
       parentheses around its arguments.  (The syntax descriptions omit the
       parentheses.)  If you use the parentheses, the simple (but occasionally
       surprising) rule is this: It looks like a function, therefore it is a
       function, and precedence doesn't matter.	 Otherwise it's a list
       operator or unary operator, and precedence does matter.	And whitespace
       between the function and left parenthesis doesn't count--so you need to
       be careful sometimes:

	   print 1+2+4;	       # Prints 7.
	   print(1+2) + 4;     # Prints 3.
	   print (1+2)+4;      # Also prints 3!
	   print +(1+2)+4;     # Prints 7.
	   print ((1+2)+4);    # Prints 7.

       If you run Perl with the -w switch it can warn you about this.  For
       example, the third line above produces:

	   print (...) interpreted as function at - line 1.
	   Useless use of integer addition in void context at - line 1.

       A few functions take no arguments at all, and therefore work as neither
       unary nor list operators.  These include such functions as "time" and
       "endpwent".  For example, "time+86_400" always means "time() + 86_400".

       For functions that can be used in either a scalar or list context,
       nonabortive failure is generally indicated in a scalar context by
       returning the undefined value, and in a list context by returning the
       null list.

       Remember the following important rule: There is no rule that relates
       the behavior of an expression in list context to its behavior in scalar
       context, or vice versa.	It might do two totally different things.
       Each operator and function decides which sort of value it would be most
       appropriate to return in scalar context.	 Some operators return the
       length of the list that would have been returned in list context.  Some
       operators return the first value in the list.  Some operators return
       the last value in the list.  Some operators return a count of
       successful operations.  In general, they do what you want, unless you
       want consistency.

       A named array in scalar context is quite different from what would at
       first glance appear to be a list in scalar context.  You can't get a
       list like "(1,2,3)" into being in scalar context, because the compiler
       knows the context at compile time.  It would generate the scalar comma
       operator there, not the list construction version of the comma.	That
       means it was never a list to start with.

       In general, functions in Perl that serve as wrappers for system calls
       of the same name (like chown(2), fork(2), closedir(2), etc.) all return
       true when they succeed and "undef" otherwise, as is usually mentioned
       in the descriptions below.  This is different from the C interfaces,
       which return "-1" on failure.  Exceptions to this rule are "wait",
       "waitpid", and "syscall".  System calls also set the special $!
       variable on failure.  Other functions do not, except accidentally.

   Perl Functions by Category
       Here are Perl's functions (including things that look like functions,
       like some keywords and named operators) arranged by category.  Some
       functions appear in more than one place.

       Functions for SCALARs or strings
	   "chomp", "chop", "chr", "crypt", "hex", "index", "lc", "lcfirst",
	   "length", "oct", "ord", "pack", "q//", "qq//", "reverse", "rindex",
	   "sprintf", "substr", "tr///", "uc", "ucfirst", "y///"

       Regular expressions and pattern matching
	   "m//", "pos", "quotemeta", "s///", "split", "study", "qr//"

       Numeric functions
	   "abs", "atan2", "cos", "exp", "hex", "int", "log", "oct", "rand",
	   "sin", "sqrt", "srand"

       Functions for real @ARRAYs
	   "pop", "push", "shift", "splice", "unshift"

       Functions for list data
	   "grep", "join", "map", "qw//", "reverse", "sort", "unpack"

       Functions for real %HASHes
	   "delete", "each", "exists", "keys", "values"

       Input and output functions
	   "binmode", "close", "closedir", "dbmclose", "dbmopen", "die",
	   "eof", "fileno", "flock", "format", "getc", "print", "printf",
	   "read", "readdir", "rewinddir", "say", "seek", "seekdir", "select",
	   "syscall", "sysread", "sysseek", "syswrite", "tell", "telldir",
	   "truncate", "warn", "write"

       Functions for fixed length data or records
	   "pack", "read", "syscall", "sysread", "syswrite", "unpack", "vec"

       Functions for filehandles, files, or directories
	   "-X", "chdir", "chmod", "chown", "chroot", "fcntl", "glob",
	   "ioctl", "link", "lstat", "mkdir", "open", "opendir", "readlink",
	   "rename", "rmdir", "stat", "symlink", "sysopen", "umask", "unlink",
	   "utime"

       Keywords related to the control flow of your Perl program
	   "caller", "continue", "die", "do", "dump", "eval", "exit", "goto",
	   "last", "next", "redo", "return", "sub", "wantarray"

       Keywords related to switch
	   "break", "continue", "given", "when", "default"

	   (These are only available if you enable the "switch" feature.  See
	   feature and "Switch statements" in perlsyn.)

       Keywords related to scoping
	   "caller", "import", "local", "my", "our", "state", "package", "use"

	   ("state" is only available if the "state" feature is enabled. See
	   feature.)

       Miscellaneous functions
	   "defined", "dump", "eval", "formline", "local", "my", "our",
	   "reset", "scalar", "state", "undef", "wantarray"

       Functions for processes and process groups
	   "alarm", "exec", "fork", "getpgrp", "getppid", "getpriority",
	   "kill", "pipe", "qx//", "setpgrp", "setpriority", "sleep",
	   "system", "times", "wait", "waitpid"

       Keywords related to perl modules
	   "do", "import", "no", "package", "require", "use"

       Keywords related to classes and object-orientation
	   "bless", "dbmclose", "dbmopen", "package", "ref", "tie", "tied",
	   "untie", "use"

       Low-level socket functions
	   "accept", "bind", "connect", "getpeername", "getsockname",
	   "getsockopt", "listen", "recv", "send", "setsockopt", "shutdown",
	   "socket", "socketpair"

       System V interprocess communication functions
	   "msgctl", "msgget", "msgrcv", "msgsnd", "semctl", "semget",
	   "semop", "shmctl", "shmget", "shmread", "shmwrite"

       Fetching user and group info
	   "endgrent", "endhostent", "endnetent", "endpwent", "getgrent",
	   "getgrgid", "getgrnam", "getlogin", "getpwent", "getpwnam",
	   "getpwuid", "setgrent", "setpwent"

       Fetching network info
	   "endprotoent", "endservent", "gethostbyaddr", "gethostbyname",
	   "gethostent", "getnetbyaddr", "getnetbyname", "getnetent",
	   "getprotobyname", "getprotobynumber", "getprotoent",
	   "getservbyname", "getservbyport", "getservent", "sethostent",
	   "setnetent", "setprotoent", "setservent"

       Time-related functions
	   "gmtime", "localtime", "time", "times"

       Functions new in perl5
	   "abs", "bless", "break", "chomp", "chr", "continue", "default",
	   "exists", "formline", "given", "glob", "import", "lc", "lcfirst",
	   "lock", "map", "my", "no", "our", "prototype", "qr//", "qw//",
	   "qx//", "readline", "readpipe", "ref", "sub"*, "sysopen", "tie",
	   "tied", "uc", "ucfirst", "untie", "use", "when"

	   * - "sub" was a keyword in perl4, but in perl5 it is an operator,
	   which can be used in expressions.

       Functions obsoleted in perl5
	   "dbmclose", "dbmopen"

   Portability
       Perl was born in Unix and can therefore access all common Unix system
       calls.  In non-Unix environments, the functionality of some Unix system
       calls may not be available, or details of the available functionality
       may differ slightly.  The Perl functions affected by this are:

       "-X", "binmode", "chmod", "chown", "chroot", "crypt", "dbmclose",
       "dbmopen", "dump", "endgrent", "endhostent", "endnetent",
       "endprotoent", "endpwent", "endservent", "exec", "fcntl", "flock",
       "fork", "getgrent", "getgrgid", "gethostbyname", "gethostent",
       "getlogin", "getnetbyaddr", "getnetbyname", "getnetent", "getppid",
       "getpgrp", "getpriority", "getprotobynumber", "getprotoent",
       "getpwent", "getpwnam", "getpwuid", "getservbyport", "getservent",
       "getsockopt", "glob", "ioctl", "kill", "link", "lstat", "msgctl",
       "msgget", "msgrcv", "msgsnd", "open", "pipe", "readlink", "rename",
       "select", "semctl", "semget", "semop", "setgrent", "sethostent",
       "setnetent", "setpgrp", "setpriority", "setprotoent", "setpwent",
       "setservent", "setsockopt", "shmctl", "shmget", "shmread", "shmwrite",
       "socket", "socketpair", "stat", "symlink", "syscall", "sysopen",
       "system", "times", "truncate", "umask", "unlink", "utime", "wait",
       "waitpid"

       For more information about the portability of these functions, see
       perlport and other available platform-specific documentation.

   Alphabetical Listing of Perl Functions
       -X FILEHANDLE
       -X EXPR
       -X DIRHANDLE
       -X      A file test, where X is one of the letters listed below.	 This
	       unary operator takes one argument, either a filename, a
	       filehandle, or a dirhandle, and tests the associated file to
	       see if something is true about it.  If the argument is omitted,
	       tests $_, except for "-t", which tests STDIN.  Unless otherwise
	       documented, it returns 1 for true and '' for false, or the
	       undefined value if the file doesn't exist.  Despite the funny
	       names, precedence is the same as any other named unary
	       operator.  The operator may be any of:

		   -r  File is readable by effective uid/gid.
		   -w  File is writable by effective uid/gid.
		   -x  File is executable by effective uid/gid.
		   -o  File is owned by effective uid.

		   -R  File is readable by real uid/gid.
		   -W  File is writable by real uid/gid.
		   -X  File is executable by real uid/gid.
		   -O  File is owned by real uid.

		   -e  File exists.
		   -z  File has zero size (is empty).
		   -s  File has nonzero size (returns size in bytes).

		   -f  File is a plain file.
		   -d  File is a directory.
		   -l  File is a symbolic link.
		   -p  File is a named pipe (FIFO), or Filehandle is a pipe.
		   -S  File is a socket.
		   -b  File is a block special file.
		   -c  File is a character special file.
		   -t  Filehandle is opened to a tty.

		   -u  File has setuid bit set.
		   -g  File has setgid bit set.
		   -k  File has sticky bit set.

		   -T  File is an ASCII text file (heuristic guess).
		   -B  File is a "binary" file (opposite of -T).

		   -M  Script start time minus file modification time, in days.
		   -A  Same for access time.
		   -C  Same for inode change time (Unix, may differ for other platforms)

	       Example:

		   while (<>) {
		       chomp;
		       next unless -f $_;      # ignore specials
		       #...
		   }

	       The interpretation of the file permission operators "-r", "-R",
	       "-w", "-W", "-x", and "-X" is by default based solely on the
	       mode of the file and the uids and gids of the user.  There may
	       be other reasons you can't actually read, write, or execute the
	       file: for example network filesystem access controls, ACLs
	       (access control lists), read-only filesystems, and unrecognized
	       executable formats.  Note that the use of these six specific
	       operators to verify if some operation is possible is usually a
	       mistake, because it may be open to race conditions.

	       Also note that, for the superuser on the local filesystems, the
	       "-r", "-R", "-w", and "-W" tests always return 1, and "-x" and
	       "-X" return 1 if any execute bit is set in the mode.  Scripts
	       run by the superuser may thus need to do a stat() to determine
	       the actual mode of the file, or temporarily set their effective
	       uid to something else.

	       If you are using ACLs, there is a pragma called "filetest" that
	       may produce more accurate results than the bare stat() mode
	       bits.  When under the "use filetest 'access'" the above-
	       mentioned filetests will test whether the permission can (not)
	       be granted using the access() family of system calls.  Also
	       note that the "-x" and "-X" may under this pragma return true
	       even if there are no execute permission bits set (nor any extra
	       execute permission ACLs).  This strangeness is due to the
	       underlying system calls' definitions. Note also that, due to
	       the implementation of "use filetest 'access'", the "_" special
	       filehandle won't cache the results of the file tests when this
	       pragma is in effect.  Read the documentation for the "filetest"
	       pragma for more information.

	       Note that "-s/a/b/" does not do a negated substitution.	Saying
	       "-exp($foo)" still works as expected, however--only single
	       letters following a minus are interpreted as file tests.

	       The "-T" and "-B" switches work as follows.  The first block or
	       so of the file is examined for odd characters such as strange
	       control codes or characters with the high bit set.  If too many
	       strange characters (>30%) are found, it's a "-B" file;
	       otherwise it's a "-T" file.  Also, any file containing null in
	       the first block is considered a binary file.  If "-T" or "-B"
	       is used on a filehandle, the current IO buffer is examined
	       rather than the first block.  Both "-T" and "-B" return true on
	       a null file, or a file at EOF when testing a filehandle.
	       Because you have to read a file to do the "-T" test, on most
	       occasions you want to use a "-f" against the file first, as in
	       "next unless -f $file && -T $file".

	       If any of the file tests (or either the "stat" or "lstat"
	       operators) are given the special filehandle consisting of a
	       solitary underline, then the stat structure of the previous
	       file test (or stat operator) is used, saving a system call.
	       (This doesn't work with "-t", and you need to remember that
	       lstat() and "-l" will leave values in the stat structure for
	       the symbolic link, not the real file.)  (Also, if the stat
	       buffer was filled by an "lstat" call, "-T" and "-B" will reset
	       it with the results of "stat _").  Example:

		   print "Can do.\n" if -r $a || -w _ || -x _;

		   stat($filename);
		   print "Readable\n" if -r _;
		   print "Writable\n" if -w _;
		   print "Executable\n" if -x _;
		   print "Setuid\n" if -u _;
		   print "Setgid\n" if -g _;
		   print "Sticky\n" if -k _;
		   print "Text\n" if -T _;
		   print "Binary\n" if -B _;

	       As of Perl 5.9.1, as a form of purely syntactic sugar, you can
	       stack file test operators, in a way that "-f -w -x $file" is
	       equivalent to "-x $file && -w _ && -f _". (This is only syntax
	       fancy: if you use the return value of "-f $file" as an argument
	       to another filetest operator, no special magic will happen.)

       abs VALUE
       abs     Returns the absolute value of its argument.  If VALUE is
	       omitted, uses $_.

       accept NEWSOCKET,GENERICSOCKET
	       Accepts an incoming socket connect, just as the accept(2)
	       system call does.  Returns the packed address if it succeeded,
	       false otherwise.	 See the example in "Sockets: Client/Server
	       Communication" in perlipc.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened file descriptor, as determined
	       by the value of $^F.  See "$^F" in perlvar.

       alarm SECONDS
       alarm   Arranges to have a SIGALRM delivered to this process after the
	       specified number of wallclock seconds has elapsed.  If SECONDS
	       is not specified, the value stored in $_ is used. (On some
	       machines, unfortunately, the elapsed time may be up to one
	       second less or more than you specified because of how seconds
	       are counted, and process scheduling may delay the delivery of
	       the signal even further.)

	       Only one timer may be counting at once.	Each call disables the
	       previous timer, and an argument of 0 may be supplied to cancel
	       the previous timer without starting a new one.  The returned
	       value is the amount of time remaining on the previous timer.

	       For delays of finer granularity than one second, the
	       Time::HiRes module (from CPAN, and starting from Perl 5.8 part
	       of the standard distribution) provides ualarm().	 You may also
	       use Perl's four-argument version of select() leaving the first
	       three arguments undefined, or you might be able to use the
	       "syscall" interface to access setitimer(2) if your system
	       supports it. See perlfaq8 for details.

	       It is usually a mistake to intermix "alarm" and "sleep" calls.
	       ("sleep" may be internally implemented in your system with
	       "alarm")

	       If you want to use "alarm" to time out a system call you need
	       to use an "eval"/"die" pair.  You can't rely on the alarm
	       causing the system call to fail with $! set to "EINTR" because
	       Perl sets up signal handlers to restart system calls on some
	       systems.	 Using "eval"/"die" always works, modulo the caveats
	       given in "Signals" in perlipc.

		   eval {
		       local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
		       alarm $timeout;
		       $nread = sysread SOCKET, $buffer, $size;
		       alarm 0;
		   };
		   if ($@) {
		       die unless $@ eq "alarm\n";   # propagate unexpected errors
		       # timed out
		   }
		   else {
		       # didn't
		   }

	       For more information see perlipc.

       atan2 Y,X
	       Returns the arctangent of Y/X in the range -PI to PI.

	       For the tangent operation, you may use the "Math::Trig::tan"
	       function, or use the familiar relation:

		   sub tan { sin($_[0]) / cos($_[0])  }

	       The return value for "atan2(0,0)" is implementation-defined;
	       consult your atan2(3) manpage for more information.

       bind SOCKET,NAME
	       Binds a network address to a socket, just as the bind system
	       call does.  Returns true if it succeeded, false otherwise.
	       NAME should be a packed address of the appropriate type for the
	       socket.	See the examples in "Sockets: Client/Server
	       Communication" in perlipc.

       binmode FILEHANDLE, LAYER
       binmode FILEHANDLE
	       Arranges for FILEHANDLE to be read or written in "binary" or
	       "text" mode on systems where the run-time libraries distinguish
	       between binary and text files.  If FILEHANDLE is an expression,
	       the value is taken as the name of the filehandle.  Returns true
	       on success, otherwise it returns "undef" and sets $! (errno).

	       On some systems (in general, DOS and Windows-based systems)
	       binmode() is necessary when you're not working with a text
	       file.  For the sake of portability it is a good idea to always
	       use it when appropriate, and to never use it when it isn't
	       appropriate.  Also, people can set their I/O to be by default
	       UTF-8 encoded Unicode, not bytes.

	       In other words: regardless of platform, use binmode() on binary
	       data, like for example images.

	       If LAYER is present it is a single string, but may contain
	       multiple directives. The directives alter the behaviour of the
	       file handle.  When LAYER is present using binmode on a text
	       file makes sense.

	       If LAYER is omitted or specified as ":raw" the filehandle is
	       made suitable for passing binary data. This includes turning
	       off possible CRLF translation and marking it as bytes (as
	       opposed to Unicode characters).	Note that, despite what may be
	       implied in "Programming Perl" (the Camel) or elsewhere, ":raw"
	       is not simply the inverse of ":crlf" -- other layers which
	       would affect the binary nature of the stream are also disabled.
	       See PerlIO, perlrun and the discussion about the PERLIO
	       environment variable.

	       The ":bytes", ":crlf", and ":utf8", and any other directives of
	       the form ":...", are called I/O layers.	The "open" pragma can
	       be used to establish default I/O layers.	 See open.

	       The LAYER parameter of the binmode() function is described as
	       "DISCIPLINE" in "Programming Perl, 3rd Edition".	 However,
	       since the publishing of this book, by many known as "Camel
	       III", the consensus of the naming of this functionality has
	       moved from "discipline" to "layer".  All documentation of this
	       version of Perl therefore refers to "layers" rather than to
	       "disciplines".  Now back to the regularly scheduled
	       documentation...

	       To mark FILEHANDLE as UTF-8, use ":utf8" or ":encoding(utf8)".
	       ":utf8" just marks the data as UTF-8 without further checking,
	       while ":encoding(utf8)" checks the data for actually being
	       valid UTF-8. More details can be found in PerlIO::encoding.

	       In general, binmode() should be called after open() but before
	       any I/O is done on the filehandle.  Calling binmode() will
	       normally flush any pending buffered output data (and perhaps
	       pending input data) on the handle.  An exception to this is the
	       ":encoding" layer that changes the default character encoding
	       of the handle, see open.	 The ":encoding" layer sometimes needs
	       to be called in mid-stream, and it doesn't flush the stream.
	       The ":encoding" also implicitly pushes on top of itself the
	       ":utf8" layer because internally Perl will operate on UTF-8
	       encoded Unicode characters.

	       The operating system, device drivers, C libraries, and Perl
	       run-time system all work together to let the programmer treat a
	       single character ("\n") as the line terminator, irrespective of
	       the external representation.  On many operating systems, the
	       native text file representation matches the internal
	       representation, but on some platforms the external
	       representation of "\n" is made up of more than one character.

	       Mac OS, all variants of Unix, and Stream_LF files on VMS use a
	       single character to end each line in the external
	       representation of text (even though that single character is
	       CARRIAGE RETURN on Mac OS and LINE FEED on Unix and most VMS
	       files). In other systems like OS/2, DOS and the various flavors
	       of MS-Windows your program sees a "\n" as a simple "\cJ", but
	       what's stored in text files are the two characters "\cM\cJ".
	       That means that, if you don't use binmode() on these systems,
	       "\cM\cJ" sequences on disk will be converted to "\n" on input,
	       and any "\n" in your program will be converted back to "\cM\cJ"
	       on output.  This is what you want for text files, but it can be
	       disastrous for binary files.

	       Another consequence of using binmode() (on some systems) is
	       that special end-of-file markers will be seen as part of the
	       data stream.  For systems from the Microsoft family this means
	       that if your binary data contains "\cZ", the I/O subsystem will
	       regard it as the end of the file, unless you use binmode().

	       binmode() is not only important for readline() and print()
	       operations, but also when using read(), seek(), sysread(),
	       syswrite() and tell() (see perlport for more details).  See the
	       $/ and "$\" variables in perlvar for how to manually set your
	       input and output line-termination sequences.

       bless REF,CLASSNAME
       bless REF
	       This function tells the thingy referenced by REF that it is now
	       an object in the CLASSNAME package.  If CLASSNAME is omitted,
	       the current package is used.  Because a "bless" is often the
	       last thing in a constructor, it returns the reference for
	       convenience.  Always use the two-argument version if a derived
	       class might inherit the function doing the blessing.  See
	       perltoot and perlobj for more about the blessing (and
	       blessings) of objects.

	       Consider always blessing objects in CLASSNAMEs that are mixed
	       case.  Namespaces with all lowercase names are considered
	       reserved for Perl pragmata.  Builtin types have all uppercase
	       names. To prevent confusion, you may wish to avoid such package
	       names as well.  Make sure that CLASSNAME is a true value.

	       See "Perl Modules" in perlmod.

       break   Break out of a "given()" block.

	       This keyword is enabled by the "switch" feature: see feature
	       for more information.

       caller EXPR
       caller  Returns the context of the current subroutine call.  In scalar
	       context, returns the caller's package name if there is a
	       caller, that is, if we're in a subroutine or "eval" or
	       "require", and the undefined value otherwise.  In list context,
	       returns

		   # 0	       1	  2
		   ($package, $filename, $line) = caller;

	       With EXPR, it returns some extra information that the debugger
	       uses to print a stack trace.  The value of EXPR indicates how
	       many call frames to go back before the current one.

		   #  0		1	   2	  3	       4
		   ($package, $filename, $line, $subroutine, $hasargs,

		   #  5		 6	    7		 8	 9	   10
		   $wantarray, $evaltext, $is_require, $hints, $bitmask, $hinthash)
		    = caller($i);

	       Here $subroutine may be "(eval)" if the frame is not a
	       subroutine call, but an "eval".	In such a case additional
	       elements $evaltext and $is_require are set: $is_require is true
	       if the frame is created by a "require" or "use" statement,
	       $evaltext contains the text of the "eval EXPR" statement.  In
	       particular, for an "eval BLOCK" statement, $subroutine is
	       "(eval)", but $evaltext is undefined.  (Note also that each
	       "use" statement creates a "require" frame inside an "eval EXPR"
	       frame.)	$subroutine may also be "(unknown)" if this particular
	       subroutine happens to have been deleted from the symbol table.
	       $hasargs is true if a new instance of @_ was set up for the
	       frame.  $hints and $bitmask contain pragmatic hints that the
	       caller was compiled with.  The $hints and $bitmask values are
	       subject to change between versions of Perl, and are not meant
	       for external use.

	       $hinthash is a reference to a hash containing the value of
	       "%^H" when the caller was compiled, or "undef" if "%^H" was
	       empty. Do not modify the values of this hash, as they are the
	       actual values stored in the optree.

	       Furthermore, when called from within the DB package, caller
	       returns more detailed information: it sets the list variable
	       @DB::args to be the arguments with which the subroutine was
	       invoked.

	       Be aware that the optimizer might have optimized call frames
	       away before "caller" had a chance to get the information.  That
	       means that caller(N) might not return information about the
	       call frame you expect it do, for "N > 1".  In particular,
	       @DB::args might have information from the previous time
	       "caller" was called.

       chdir EXPR
       chdir FILEHANDLE
       chdir DIRHANDLE
       chdir   Changes the working directory to EXPR, if possible. If EXPR is
	       omitted, changes to the directory specified by $ENV{HOME}, if
	       set; if not, changes to the directory specified by
	       $ENV{LOGDIR}. (Under VMS, the variable $ENV{SYS$LOGIN} is also
	       checked, and used if it is set.) If neither is set, "chdir"
	       does nothing. It returns true upon success, false otherwise.
	       See the example under "die".

	       On systems that support fchdir, you might pass a file handle or
	       directory handle as argument.  On systems that don't support
	       fchdir, passing handles produces a fatal error at run time.

       chmod LIST
	       Changes the permissions of a list of files.  The first element
	       of the list must be the numerical mode, which should probably
	       be an octal number, and which definitely should not be a string
	       of octal digits: 0644 is okay, '0644' is not.  Returns the
	       number of files successfully changed.  See also "oct", if all
	       you have is a string.

		   $cnt = chmod 0755, 'foo', 'bar';
		   chmod 0755, @executables;
		   $mode = '0644'; chmod $mode, 'foo';	    # !!! sets mode to
							    # --w----r-T
		   $mode = '0644'; chmod oct($mode), 'foo'; # this is better
		   $mode = 0644;   chmod $mode, 'foo';	    # this is best

	       On systems that support fchmod, you might pass file handles
	       among the files.	 On systems that don't support fchmod, passing
	       file handles produces a fatal error at run time.	  The file
	       handles must be passed as globs or references to be recognized.
	       Barewords are considered file names.

		   open(my $fh, "<", "foo");
		   my $perm = (stat $fh)[2] & 07777;
		   chmod($perm | 0600, $fh);

	       You can also import the symbolic "S_I*" constants from the
	       Fcntl module:

		   use Fcntl ':mode';

		   chmod S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH, @executables;
		   # This is identical to the chmod 0755 of the above example.

       chomp VARIABLE
       chomp( LIST )
       chomp   This safer version of "chop" removes any trailing string that
	       corresponds to the current value of $/ (also known as
	       $INPUT_RECORD_SEPARATOR in the "English" module).  It returns
	       the total number of characters removed from all its arguments.
	       It's often used to remove the newline from the end of an input
	       record when you're worried that the final record may be missing
	       its newline.  When in paragraph mode ("$/ = """), it removes
	       all trailing newlines from the string.  When in slurp mode ("$/
	       = undef") or fixed-length record mode ($/ is a reference to an
	       integer or the like, see perlvar) chomp() won't remove
	       anything.  If VARIABLE is omitted, it chomps $_.	 Example:

		   while (<>) {
		       chomp;  # avoid \n on last field
		       @array = split(/:/);
		       # ...
		   }

	       If VARIABLE is a hash, it chomps the hash's values, but not its
	       keys.

	       You can actually chomp anything that's an lvalue, including an
	       assignment:

		   chomp($cwd = `pwd`);
		   chomp($answer = <STDIN>);

	       If you chomp a list, each element is chomped, and the total
	       number of characters removed is returned.

	       Note that parentheses are necessary when you're chomping
	       anything that is not a simple variable.	This is because "chomp
	       $cwd = `pwd`;" is interpreted as "(chomp $cwd) = `pwd`;",
	       rather than as "chomp( $cwd = `pwd` )" which you might expect.
	       Similarly, "chomp $a, $b" is interpreted as "chomp($a), $b"
	       rather than as "chomp($a, $b)".

       chop VARIABLE
       chop( LIST )
       chop    Chops off the last character of a string and returns the
	       character chopped.  It is much more efficient than "s/.$//s"
	       because it neither scans nor copies the string.	If VARIABLE is
	       omitted, chops $_.  If VARIABLE is a hash, it chops the hash's
	       values, but not its keys.

	       You can actually chop anything that's an lvalue, including an
	       assignment.

	       If you chop a list, each element is chopped.  Only the value of
	       the last "chop" is returned.

	       Note that "chop" returns the last character.  To return all but
	       the last character, use "substr($string, 0, -1)".

	       See also "chomp".

       chown LIST
	       Changes the owner (and group) of a list of files.  The first
	       two elements of the list must be the numeric uid and gid, in
	       that order.  A value of -1 in either position is interpreted by
	       most systems to leave that value unchanged.  Returns the number
	       of files successfully changed.

		   $cnt = chown $uid, $gid, 'foo', 'bar';
		   chown $uid, $gid, @filenames;

	       On systems that support fchown, you might pass file handles
	       among the files.	 On systems that don't support fchown, passing
	       file handles produces a fatal error at run time.	 The file
	       handles must be passed as globs or references to be recognized.
	       Barewords are considered file names.

	       Here's an example that looks up nonnumeric uids in the passwd
	       file:

		   print "User: ";
		   chomp($user = <STDIN>);
		   print "Files: ";
		   chomp($pattern = <STDIN>);

		   ($login,$pass,$uid,$gid) = getpwnam($user)
		       or die "$user not in passwd file";

		   @ary = glob($pattern);      # expand filenames
		   chown $uid, $gid, @ary;

	       On most systems, you are not allowed to change the ownership of
	       the file unless you're the superuser, although you should be
	       able to change the group to any of your secondary groups.  On
	       insecure systems, these restrictions may be relaxed, but this
	       is not a portable assumption.  On POSIX systems, you can detect
	       this condition this way:

		   use POSIX qw(sysconf _PC_CHOWN_RESTRICTED);
		   $can_chown_giveaway = not sysconf(_PC_CHOWN_RESTRICTED);

       chr NUMBER
       chr     Returns the character represented by that NUMBER in the
	       character set.  For example, "chr(65)" is "A" in either ASCII
	       or Unicode, and chr(0x263a) is a Unicode smiley face.

	       Negative values give the Unicode replacement character
	       (chr(0xfffd)), except under the bytes pragma, where low eight
	       bits of the value (truncated to an integer) are used.

	       If NUMBER is omitted, uses $_.

	       For the reverse, use "ord".

	       Note that characters from 128 to 255 (inclusive) are by default
	       internally not encoded as UTF-8 for backward compatibility
	       reasons.

	       See perlunicode for more about Unicode.

       chroot FILENAME
       chroot  This function works like the system call by the same name: it
	       makes the named directory the new root directory for all
	       further pathnames that begin with a "/" by your process and all
	       its children.  (It doesn't change your current working
	       directory, which is unaffected.)	 For security reasons, this
	       call is restricted to the superuser.  If FILENAME is omitted,
	       does a "chroot" to $_.

       close FILEHANDLE
       close   Closes the file or pipe associated with the file handle,
	       flushes the IO buffers, and closes the system file descriptor.
	       Returns true if those operations have succeeded and if no error
	       was reported by any PerlIO layer.  Closes the currently
	       selected filehandle if the argument is omitted.

	       You don't have to close FILEHANDLE if you are immediately going
	       to do another "open" on it, because "open" will close it for
	       you.  (See "open".)  However, an explicit "close" on an input
	       file resets the line counter ($.), while the implicit close
	       done by "open" does not.

	       If the file handle came from a piped open, "close" will
	       additionally return false if one of the other system calls
	       involved fails, or if the program exits with non-zero status.
	       (If the only problem was that the program exited non-zero, $!
	       will be set to 0.)  Closing a pipe also waits for the process
	       executing on the pipe to complete, in case you want to look at
	       the output of the pipe afterwards, and implicitly puts the exit
	       status value of that command into $? and
	       "${^CHILD_ERROR_NATIVE}".

	       Prematurely closing the read end of a pipe (i.e. before the
	       process writing to it at the other end has closed it) will
	       result in a SIGPIPE being delivered to the writer.  If the
	       other end can't handle that, be sure to read all the data
	       before closing the pipe.

	       Example:

		   open(OUTPUT, '|sort >foo')  # pipe to sort
		       or die "Can't start sort: $!";
		   #...			       # print stuff to output
		   close OUTPUT		       # wait for sort to finish
		       or warn $! ? "Error closing sort pipe: $!"
				  : "Exit status $? from sort";
		   open(INPUT, 'foo')	       # get sort's results
		       or die "Can't open 'foo' for input: $!";

	       FILEHANDLE may be an expression whose value can be used as an
	       indirect filehandle, usually the real filehandle name.

       closedir DIRHANDLE
	       Closes a directory opened by "opendir" and returns the success
	       of that system call.

       connect SOCKET,NAME
	       Attempts to connect to a remote socket, just as the connect
	       system call does.  Returns true if it succeeded, false
	       otherwise.  NAME should be a packed address of the appropriate
	       type for the socket.  See the examples in "Sockets:
	       Client/Server Communication" in perlipc.

       continue BLOCK
       continue
	       "continue" is actually a flow control statement rather than a
	       function.  If there is a "continue" BLOCK attached to a BLOCK
	       (typically in a "while" or "foreach"), it is always executed
	       just before the conditional is about to be evaluated again,
	       just like the third part of a "for" loop in C.  Thus it can be
	       used to increment a loop variable, even when the loop has been
	       continued via the "next" statement (which is similar to the C
	       "continue" statement).

	       "last", "next", or "redo" may appear within a "continue" block.
	       "last" and "redo" will behave as if they had been executed
	       within the main block.  So will "next", but since it will
	       execute a "continue" block, it may be more entertaining.

		   while (EXPR) {
		       ### redo always comes here
		       do_something;
		   } continue {
		       ### next always comes here
		       do_something_else;
		       # then back the top to re-check EXPR
		   }
		   ### last always comes here

	       Omitting the "continue" section is semantically equivalent to
	       using an empty one, logically enough.  In that case, "next"
	       goes directly back to check the condition at the top of the
	       loop.

	       If the "switch" feature is enabled, "continue" is also a
	       function that will break out of the current "when" or "default"
	       block, and fall through to the next case. See feature and
	       "Switch statements" in perlsyn for more information.

       cos EXPR
       cos     Returns the cosine of EXPR (expressed in radians).  If EXPR is
	       omitted, takes cosine of $_.

	       For the inverse cosine operation, you may use the
	       "Math::Trig::acos()" function, or use this relation:

		   sub acos { atan2( sqrt(1 - $_[0] * $_[0]), $_[0] ) }

       crypt PLAINTEXT,SALT
	       Creates a digest string exactly like the crypt(3) function in
	       the C library (assuming that you actually have a version there
	       that has not been extirpated as a potential munition).

	       crypt() is a one-way hash function.  The PLAINTEXT and SALT is
	       turned into a short string, called a digest, which is returned.
	       The same PLAINTEXT and SALT will always return the same string,
	       but there is no (known) way to get the original PLAINTEXT from
	       the hash.  Small changes in the PLAINTEXT or SALT will result
	       in large changes in the digest.

	       There is no decrypt function.  This function isn't all that
	       useful for cryptography (for that, look for Crypt modules on
	       your nearby CPAN mirror) and the name "crypt" is a bit of a
	       misnomer.  Instead it is primarily used to check if two pieces
	       of text are the same without having to transmit or store the
	       text itself.  An example is checking if a correct password is
	       given.  The digest of the password is stored, not the password
	       itself.	The user types in a password that is crypt()'d with
	       the same salt as the stored digest.  If the two digests match
	       the password is correct.

	       When verifying an existing digest string you should use the
	       digest as the salt (like "crypt($plain, $digest) eq $digest").
	       The SALT used to create the digest is visible as part of the
	       digest.	This ensures crypt() will hash the new string with the
	       same salt as the digest.	 This allows your code to work with
	       the standard crypt and with more exotic implementations.	 In
	       other words, do not assume anything about the returned string
	       itself, or how many bytes in the digest matter.

	       Traditionally the result is a string of 13 bytes: two first
	       bytes of the salt, followed by 11 bytes from the set
	       "[./0-9A-Za-z]", and only the first eight bytes of PLAINTEXT
	       mattered. But alternative hashing schemes (like MD5), higher
	       level security schemes (like C2), and implementations on non-
	       UNIX platforms may produce different strings.

	       When choosing a new salt create a random two character string
	       whose characters come from the set "[./0-9A-Za-z]" (like "join
	       '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]").
	       This set of characters is just a recommendation; the characters
	       allowed in the salt depend solely on your system's crypt
	       library, and Perl can't restrict what salts "crypt()" accepts.

	       Here's an example that makes sure that whoever runs this
	       program knows their password:

		   $pwd = (getpwuid($<))[1];

		   system "stty -echo";
		   print "Password: ";
		   chomp($word = <STDIN>);
		   print "\n";
		   system "stty echo";

		   if (crypt($word, $pwd) ne $pwd) {
		       die "Sorry...\n";
		   } else {
		       print "ok\n";
		   }

	       Of course, typing in your own password to whoever asks you for
	       it is unwise.

	       The crypt function is unsuitable for hashing large quantities
	       of data, not least of all because you can't get the information
	       back.  Look at the Digest module for more robust algorithms.

	       If using crypt() on a Unicode string (which potentially has
	       characters with codepoints above 255), Perl tries to make sense
	       of the situation by trying to downgrade (a copy of the string)
	       the string back to an eight-bit byte string before calling
	       crypt() (on that copy).	If that works, good.  If not, crypt()
	       dies with "Wide character in crypt".

       dbmclose HASH
	       [This function has been largely superseded by the "untie"
	       function.]

	       Breaks the binding between a DBM file and a hash.

       dbmopen HASH,DBNAME,MASK
	       [This function has been largely superseded by the "tie"
	       function.]

	       This binds a dbm(3), ndbm(3), sdbm(3), gdbm(3), or Berkeley DB
	       file to a hash.	HASH is the name of the hash.  (Unlike normal
	       "open", the first argument is not a filehandle, even though it
	       looks like one).	 DBNAME is the name of the database (without
	       the .dir or .pag extension if any).  If the database does not
	       exist, it is created with protection specified by MASK (as
	       modified by the "umask").  If your system supports only the
	       older DBM functions, you may perform only one "dbmopen" in your
	       program.	 In older versions of Perl, if your system had neither
	       DBM nor ndbm, calling "dbmopen" produced a fatal error; it now
	       falls back to sdbm(3).

	       If you don't have write access to the DBM file, you can only
	       read hash variables, not set them.  If you want to test whether
	       you can write, either use file tests or try setting a dummy
	       hash entry inside an "eval", which will trap the error.

	       Note that functions such as "keys" and "values" may return huge
	       lists when used on large DBM files.  You may prefer to use the
	       "each" function to iterate over large DBM files.	 Example:

		   # print out history file offsets
		   dbmopen(%HIST,'/usr/lib/news/history',0666);
		   while (($key,$val) = each %HIST) {
		       print $key, ' = ', unpack('L',$val), "\n";
		   }
		   dbmclose(%HIST);

	       See also AnyDBM_File for a more general description of the pros
	       and cons of the various dbm approaches, as well as DB_File for
	       a particularly rich implementation.

	       You can control which DBM library you use by loading that
	       library before you call dbmopen():

		   use DB_File;
		   dbmopen(%NS_Hist, "$ENV{HOME}/.netscape/history.db")
		       or die "Can't open netscape history file: $!";

       defined EXPR
       defined Returns a Boolean value telling whether EXPR has a value other
	       than the undefined value "undef".  If EXPR is not present, $_
	       will be checked.

	       Many operations return "undef" to indicate failure, end of
	       file, system error, uninitialized variable, and other
	       exceptional conditions.	This function allows you to
	       distinguish "undef" from other values.  (A simple Boolean test
	       will not distinguish among "undef", zero, the empty string, and
	       "0", which are all equally false.)  Note that since "undef" is
	       a valid scalar, its presence doesn't necessarily indicate an
	       exceptional condition: "pop" returns "undef" when its argument
	       is an empty array, or when the element to return happens to be
	       "undef".

	       You may also use "defined(&func)" to check whether subroutine
	       &func has ever been defined.  The return value is unaffected by
	       any forward declarations of &func.  Note that a subroutine
	       which is not defined may still be callable: its package may
	       have an "AUTOLOAD" method that makes it spring into existence
	       the first time that it is called -- see perlsub.

	       Use of "defined" on aggregates (hashes and arrays) is
	       deprecated.  It used to report whether memory for that
	       aggregate has ever been allocated.  This behavior may disappear
	       in future versions of Perl.  You should instead use a simple
	       test for size:

		   if (@an_array) { print "has array elements\n" }
		   if (%a_hash)	  { print "has hash members\n"	 }

	       When used on a hash element, it tells you whether the value is
	       defined, not whether the key exists in the hash.	 Use "exists"
	       for the latter purpose.

	       Examples:

		   print if defined $switch{'D'};
		   print "$val\n" while defined($val = pop(@ary));
		   die "Can't readlink $sym: $!"
		       unless defined($value = readlink $sym);
		   sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }
		   $debugging = 0 unless defined $debugging;

	       Note:  Many folks tend to overuse "defined", and then are
	       surprised to discover that the number 0 and "" (the zero-length
	       string) are, in fact, defined values.  For example, if you say

		   "ab" =~ /a(.*)b/;

	       The pattern match succeeds, and $1 is defined, despite the fact
	       that it matched "nothing".  It didn't really fail to match
	       anything.  Rather, it matched something that happened to be
	       zero characters long.  This is all very above-board and honest.
	       When a function returns an undefined value, it's an admission
	       that it couldn't give you an honest answer.  So you should use
	       "defined" only when you're questioning the integrity of what
	       you're trying to do.  At other times, a simple comparison to 0
	       or "" is what you want.

	       See also "undef", "exists", "ref".

       delete EXPR
	       Given an expression that specifies a hash element, array
	       element, hash slice, or array slice, deletes the specified
	       element(s) from the hash or array.  In the case of an array, if
	       the array elements happen to be at the end, the size of the
	       array will shrink to the highest element that tests true for
	       exists() (or 0 if no such element exists).

	       Returns a list with the same number of elements as the number
	       of elements for which deletion was attempted.  Each element of
	       that list consists of either the value of the element deleted,
	       or the undefined value.	In scalar context, this means that you
	       get the value of the last element deleted (or the undefined
	       value if that element did not exist).

		   %hash = (foo => 11, bar => 22, baz => 33);
		   $scalar = delete $hash{foo};		    # $scalar is 11
		   $scalar = delete @hash{qw(foo bar)};	    # $scalar is 22
		   @array  = delete @hash{qw(foo bar baz)}; # @array  is (undef,undef,33)

	       Deleting from %ENV modifies the environment.  Deleting from a
	       hash tied to a DBM file deletes the entry from the DBM file.
	       Deleting from a "tie"d hash or array may not necessarily return
	       anything.

	       Deleting an array element effectively returns that position of
	       the array to its initial, uninitialized state.  Subsequently
	       testing for the same element with exists() will return false.
	       Also, deleting array elements in the middle of an array will
	       not shift the index of the elements after them down.  Use
	       splice() for that.  See "exists".

	       The following (inefficiently) deletes all the values of %HASH
	       and @ARRAY:

		   foreach $key (keys %HASH) {
		       delete $HASH{$key};
		   }

		   foreach $index (0 .. $#ARRAY) {
		       delete $ARRAY[$index];
		   }

	       And so do these:

		   delete @HASH{keys %HASH};

		   delete @ARRAY[0 .. $#ARRAY];

	       But both of these are slower than just assigning the empty list
	       or undefining %HASH or @ARRAY:

		   %HASH = ();	       # completely empty %HASH
		   undef %HASH;	       # forget %HASH ever existed

		   @ARRAY = ();	       # completely empty @ARRAY
		   undef @ARRAY;       # forget @ARRAY ever existed

	       Note that the EXPR can be arbitrarily complicated as long as
	       the final operation is a hash element, array element,  hash
	       slice, or array slice lookup:

		   delete $ref->[$x][$y]{$key};
		   delete @{$ref->[$x][$y]}{$key1, $key2, @morekeys};

		   delete $ref->[$x][$y][$index];
		   delete @{$ref->[$x][$y]}[$index1, $index2, @moreindices];

       die LIST
	       Outside an "eval", prints the value of LIST to "STDERR" and
	       exits with the current value of $! (errno).  If $! is 0, exits
	       with the value of "($? >> 8)" (backtick `command` status).  If
	       "($? >> 8)" is 0, exits with 255.  Inside an "eval()," the
	       error message is stuffed into $@ and the "eval" is terminated
	       with the undefined value.  This makes "die" the way to raise an
	       exception.

	       Equivalent examples:

		   die "Can't cd to spool: $!\n" unless chdir '/usr/spool/news';
		   chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"

	       If the last element of LIST does not end in a newline, the
	       current script line number and input line number (if any) are
	       also printed, and a newline is supplied.	 Note that the "input
	       line number" (also known as "chunk") is subject to whatever
	       notion of "line" happens to be currently in effect, and is also
	       available as the special variable $..  See "$/" in perlvar and
	       "$." in perlvar.

	       Hint: sometimes appending ", stopped" to your message will
	       cause it to make better sense when the string "at foo line 123"
	       is appended.  Suppose you are running script "canasta".

		   die "/etc/games is no good";
		   die "/etc/games is no good, stopped";

	       produce, respectively

		   /etc/games is no good at canasta line 123.
		   /etc/games is no good, stopped at canasta line 123.

	       See also exit(), warn(), and the Carp module.

	       If LIST is empty and $@ already contains a value (typically
	       from a previous eval) that value is reused after appending
	       "\t...propagated".  This is useful for propagating exceptions:

		   eval { ... };
		   die unless $@ =~ /Expected exception/;

	       If LIST is empty and $@ contains an object reference that has a
	       "PROPAGATE" method, that method will be called with additional
	       file and line number parameters.	 The return value replaces the
	       value in $@.  i.e. as if "$@ = eval { $@->PROPAGATE(__FILE__,
	       __LINE__) };" were called.

	       If $@ is empty then the string "Died" is used.

	       die() can also be called with a reference argument.  If this
	       happens to be trapped within an eval(), $@ contains the
	       reference.  This behavior permits a more elaborate exception
	       handling implementation using objects that maintain arbitrary
	       state about the nature of the exception.	 Such a scheme is
	       sometimes preferable to matching particular string values of $@
	       using regular expressions.  Because $@ is a global variable,
	       and eval() may be used within object implementations, care must
	       be taken that analyzing the error object doesn't replace the
	       reference in the global variable.  The easiest solution is to
	       make a local copy of the reference before doing other
	       manipulations.  Here's an example:

		   use Scalar::Util 'blessed';

		   eval { ... ; die Some::Module::Exception->new( FOO => "bar" ) };
		   if (my $ev_err = $@) {
		       if (blessed($ev_err) && $ev_err->isa("Some::Module::Exception")) {
			   # handle Some::Module::Exception
		       }
		       else {
			   # handle all other possible exceptions
		       }
		   }

	       Because perl will stringify uncaught exception messages before
	       displaying them, you may want to overload stringification
	       operations on such custom exception objects.  See overload for
	       details about that.

	       You can arrange for a callback to be run just before the "die"
	       does its deed, by setting the $SIG{__DIE__} hook.  The
	       associated handler will be called with the error text and can
	       change the error message, if it sees fit, by calling "die"
	       again.  See "$SIG{expr}" in perlvar for details on setting %SIG
	       entries, and "eval BLOCK" for some examples.  Although this
	       feature was to be run only right before your program was to
	       exit, this is not currently the case--the $SIG{__DIE__} hook is
	       currently called even inside eval()ed blocks/strings!  If one
	       wants the hook to do nothing in such situations, put

		       die @_ if $^S;

	       as the first line of the handler (see "$^S" in perlvar).
	       Because this promotes strange action at a distance, this
	       counterintuitive behavior may be fixed in a future release.

       do BLOCK
	       Not really a function.  Returns the value of the last command
	       in the sequence of commands indicated by BLOCK.	When modified
	       by the "while" or "until" loop modifier, executes the BLOCK
	       once before testing the loop condition. (On other statements
	       the loop modifiers test the conditional first.)

	       "do BLOCK" does not count as a loop, so the loop control
	       statements "next", "last", or "redo" cannot be used to leave or
	       restart the block.  See perlsyn for alternative strategies.

       do SUBROUTINE(LIST)
	       This form of subroutine call is deprecated.  See perlsub.

       do EXPR Uses the value of EXPR as a filename and executes the contents
	       of the file as a Perl script.

		   do 'stat.pl';

	       is just like

		   eval `cat stat.pl`;

	       except that it's more efficient and concise, keeps track of the
	       current filename for error messages, searches the @INC
	       directories, and updates %INC if the file is found.  See
	       "Predefined Names" in perlvar for these variables.  It also
	       differs in that code evaluated with "do FILENAME" cannot see
	       lexicals in the enclosing scope; "eval STRING" does.  It's the
	       same, however, in that it does reparse the file every time you
	       call it, so you probably don't want to do this inside a loop.

	       If "do" cannot read the file, it returns undef and sets $! to
	       the error.  If "do" can read the file but cannot compile it, it
	       returns undef and sets an error message in $@.	If the file is
	       successfully compiled, "do" returns the value of the last
	       expression evaluated.

	       Note that inclusion of library modules is better done with the
	       "use" and "require" operators, which also do automatic error
	       checking and raise an exception if there's a problem.

	       You might like to use "do" to read in a program configuration
	       file.  Manual error checking can be done this way:

		   # read in config files: system first, then user
		   for $file ("/share/prog/defaults.rc",
			      "$ENV{HOME}/.someprogrc")
		  {
		       unless ($return = do $file) {
			   warn "couldn't parse $file: $@" if $@;
			   warn "couldn't do $file: $!"	   unless defined $return;
			   warn "couldn't run $file"	   unless $return;
		       }
		   }

       dump LABEL
       dump    This function causes an immediate core dump.  See also the -u
	       command-line switch in perlrun, which does the same thing.
	       Primarily this is so that you can use the undump program (not
	       supplied) to turn your core dump into an executable binary
	       after having initialized all your variables at the beginning of
	       the program.  When the new binary is executed it will begin by
	       executing a "goto LABEL" (with all the restrictions that "goto"
	       suffers).  Think of it as a goto with an intervening core dump
	       and reincarnation.  If "LABEL" is omitted, restarts the program
	       from the top.

	       WARNING: Any files opened at the time of the dump will not be
	       open any more when the program is reincarnated, with possible
	       resulting confusion on the part of Perl.

	       This function is now largely obsolete, mostly because it's very
	       hard to convert a core file into an executable. That's why you
	       should now invoke it as "CORE::dump()", if you don't want to be
	       warned against a possible typo.

       each HASH
	       When called in list context, returns a 2-element list
	       consisting of the key and value for the next element of a hash,
	       so that you can iterate over it.	 When called in scalar
	       context, returns only the key for the next element in the hash.

	       Entries are returned in an apparently random order.  The actual
	       random order is subject to change in future versions of perl,
	       but it is guaranteed to be in the same order as either the
	       "keys" or "values" function would produce on the same
	       (unmodified) hash.  Since Perl 5.8.2 the ordering can be
	       different even between different runs of Perl for security
	       reasons (see "Algorithmic Complexity Attacks" in perlsec).

	       When the hash is entirely read, a null array is returned in
	       list context (which when assigned produces a false (0) value),
	       and "undef" in scalar context.  The next call to "each" after
	       that will start iterating again.	 There is a single iterator
	       for each hash, shared by all "each", "keys", and "values"
	       function calls in the program; it can be reset by reading all
	       the elements from the hash, or by evaluating "keys HASH" or
	       "values HASH".  If you add or delete elements of a hash while
	       you're iterating over it, you may get entries skipped or
	       duplicated, so don't.  Exception: It is always safe to delete
	       the item most recently returned by "each()", which means that
	       the following code will work:

		       while (($key, $value) = each %hash) {
			 print $key, "\n";
			 delete $hash{$key};   # This is safe
		       }

	       The following prints out your environment like the printenv(1)
	       program, only in a different order:

		   while (($key,$value) = each %ENV) {
		       print "$key=$value\n";
		   }

	       See also "keys", "values" and "sort".

       eof FILEHANDLE
       eof ()
       eof     Returns 1 if the next read on FILEHANDLE will return end of
	       file, or if FILEHANDLE is not open.  FILEHANDLE may be an
	       expression whose value gives the real filehandle.  (Note that
	       this function actually reads a character and then "ungetc"s it,
	       so isn't very useful in an interactive context.)	 Do not read
	       from a terminal file (or call "eof(FILEHANDLE)" on it) after
	       end-of-file is reached.	File types such as terminals may lose
	       the end-of-file condition if you do.

	       An "eof" without an argument uses the last file read.  Using
	       "eof()" with empty parentheses is very different.  It refers to
	       the pseudo file formed from the files listed on the command
	       line and accessed via the "<>" operator.	 Since "<>" isn't
	       explicitly opened, as a normal filehandle is, an "eof()" before
	       "<>" has been used will cause @ARGV to be examined to determine
	       if input is available.	Similarly, an "eof()" after "<>" has
	       returned end-of-file will assume you are processing another
	       @ARGV list, and if you haven't set @ARGV, will read input from
	       "STDIN"; see "I/O Operators" in perlop.

	       In a "while (<>)" loop, "eof" or "eof(ARGV)" can be used to
	       detect the end of each file, "eof()" will only detect the end
	       of the last file.  Examples:

		   # reset line numbering on each input file
		   while (<>) {
		       next if /^\s*#/;	       # skip comments
		       print "$.\t$_";
		   } continue {
		       close ARGV  if eof;     # Not eof()!
		   }

		   # insert dashes just before last line of last file
		   while (<>) {
		       if (eof()) {	       # check for end of last file
			   print "--------------\n";
		       }
		       print;
		       last if eof();	       # needed if we're reading from a terminal
		   }

	       Practical hint: you almost never need to use "eof" in Perl,
	       because the input operators typically return "undef" when they
	       run out of data, or if there was an error.

       eval EXPR
       eval BLOCK
       eval    In the first form, the return value of EXPR is parsed and
	       executed as if it were a little Perl program.  The value of the
	       expression (which is itself determined within scalar context)
	       is first parsed, and if there weren't any errors, executed in
	       the lexical context of the current Perl program, so that any
	       variable settings or subroutine and format definitions remain
	       afterwards.  Note that the value is parsed every time the
	       "eval" executes.	 If EXPR is omitted, evaluates $_.  This form
	       is typically used to delay parsing and subsequent execution of
	       the text of EXPR until run time.

	       In the second form, the code within the BLOCK is parsed only
	       once--at the same time the code surrounding the "eval" itself
	       was parsed--and executed within the context of the current Perl
	       program.	 This form is typically used to trap exceptions more
	       efficiently than the first (see below), while also providing
	       the benefit of checking the code within BLOCK at compile time.

	       The final semicolon, if any, may be omitted from the value of
	       EXPR or within the BLOCK.

	       In both forms, the value returned is the value of the last
	       expression evaluated inside the mini-program; a return
	       statement may be also used, just as with subroutines.  The
	       expression providing the return value is evaluated in void,
	       scalar, or list context, depending on the context of the "eval"
	       itself.	See "wantarray" for more on how the evaluation context
	       can be determined.

	       If there is a syntax error or runtime error, or a "die"
	       statement is executed, "eval" returns an undefined value in
	       scalar context or an empty list in list context, and $@ is set
	       to the error message.  If there was no error, $@ is guaranteed
	       to be a null string.  Beware that using "eval" neither silences
	       perl from printing warnings to STDERR, nor does it stuff the
	       text of warning messages into $@.  To do either of those, you
	       have to use the $SIG{__WARN__} facility, or turn off warnings
	       inside the BLOCK or EXPR using "no warnings 'all'".  See
	       "warn", perlvar, warnings and perllexwarn.

	       Note that, because "eval" traps otherwise-fatal errors, it is
	       useful for determining whether a particular feature (such as
	       "socket" or "symlink") is implemented.  It is also Perl's
	       exception trapping mechanism, where the die operator is used to
	       raise exceptions.

	       If you want to trap errors when loading an XS module, some
	       problems with the binary interface (such as Perl version skew)
	       may be fatal even with "eval" unless $ENV{PERL_DL_NONLAZY} is
	       set. See perlrun.

	       If the code to be executed doesn't vary, you may use the eval-
	       BLOCK form to trap run-time errors without incurring the
	       penalty of recompiling each time.  The error, if any, is still
	       returned in $@.	Examples:

		   # make divide-by-zero nonfatal
		   eval { $answer = $a / $b; }; warn $@ if $@;

		   # same thing, but less efficient
		   eval '$answer = $a / $b'; warn $@ if $@;

		   # a compile-time error
		   eval { $answer = };		       # WRONG

		   # a run-time error
		   eval '$answer =';   # sets $@

	       Using the "eval{}" form as an exception trap in libraries does
	       have some issues.  Due to the current arguably broken state of
	       "__DIE__" hooks, you may wish not to trigger any "__DIE__"
	       hooks that user code may have installed.	 You can use the
	       "local $SIG{__DIE__}" construct for this purpose, as shown in
	       this example:

		   # a very private exception trap for divide-by-zero
		   eval { local $SIG{'__DIE__'}; $answer = $a / $b; };
		   warn $@ if $@;

	       This is especially significant, given that "__DIE__" hooks can
	       call "die" again, which has the effect of changing their error
	       messages:

		   # __DIE__ hooks may modify error messages
		   {
		      local $SIG{'__DIE__'} =
			     sub { (my $x = $_[0]) =~ s/foo/bar/g; die $x };
		      eval { die "foo lives here" };
		      print $@ if $@;		     # prints "bar lives here"
		   }

	       Because this promotes action at a distance, this
	       counterintuitive behavior may be fixed in a future release.

	       With an "eval", you should be especially careful to remember
	       what's being looked at when:

		   eval $x;	       # CASE 1
		   eval "$x";	       # CASE 2

		   eval '$x';	       # CASE 3
		   eval { $x };	       # CASE 4

		   eval "\$$x++";      # CASE 5
		   $$x++;	       # CASE 6

	       Cases 1 and 2 above behave identically: they run the code
	       contained in the variable $x.  (Although case 2 has misleading
	       double quotes making the reader wonder what else might be
	       happening (nothing is).)	 Cases 3 and 4 likewise behave in the
	       same way: they run the code '$x', which does nothing but return
	       the value of $x.	 (Case 4 is preferred for purely visual
	       reasons, but it also has the advantage of compiling at compile-
	       time instead of at run-time.)  Case 5 is a place where normally
	       you would like to use double quotes, except that in this
	       particular situation, you can just use symbolic references
	       instead, as in case 6.

	       The assignment to $@ occurs before restoration of localised
	       variables, which means a temporary is required if you want to
	       mask some but not all errors:

		   # alter $@ on nefarious repugnancy only
		   {
		      my $e;
		      {
			 local $@; # protect existing $@
			 eval { test_repugnancy() };
			 # $@ =~ /nefarious/ and die $@; # DOES NOT WORK
			 $@ =~ /nefarious/ and $e = $@;
		      }
		      die $e if defined $e
		   }

	       "eval BLOCK" does not count as a loop, so the loop control
	       statements "next", "last", or "redo" cannot be used to leave or
	       restart the block.

	       Note that as a very special case, an "eval ''" executed within
	       the "DB" package doesn't see the usual surrounding lexical
	       scope, but rather the scope of the first non-DB piece of code
	       that called it. You don't normally need to worry about this
	       unless you are writing a Perl debugger.

       exec LIST
       exec PROGRAM LIST
	       The "exec" function executes a system command and never
	       returns-- use "system" instead of "exec" if you want it to
	       return.	It fails and returns false only if the command does
	       not exist and it is executed directly instead of via your
	       system's command shell (see below).

	       Since it's a common mistake to use "exec" instead of "system",
	       Perl warns you if there is a following statement which isn't
	       "die", "warn", or "exit" (if "-w" is set	 -  but you always do
	       that).	If you really want to follow an "exec" with some other
	       statement, you can use one of these styles to avoid the
	       warning:

		   exec ('foo')	  or print STDERR "couldn't exec foo: $!";
		   { exec ('foo') }; print STDERR "couldn't exec foo: $!";

	       If there is more than one argument in LIST, or if LIST is an
	       array with more than one value, calls execvp(3) with the
	       arguments in LIST.  If there is only one scalar argument or an
	       array with one element in it, the argument is checked for shell
	       metacharacters, and if there are any, the entire argument is
	       passed to the system's command shell for parsing (this is
	       "/bin/sh -c" on Unix platforms, but varies on other platforms).
	       If there are no shell metacharacters in the argument, it is
	       split into words and passed directly to "execvp", which is more
	       efficient.  Examples:

		   exec '/bin/echo', 'Your arguments are: ', @ARGV;
		   exec "sort $outfile | uniq";

	       If you don't really want to execute the first argument, but
	       want to lie to the program you are executing about its own
	       name, you can specify the program you actually want to run as
	       an "indirect object" (without a comma) in front of the LIST.
	       (This always forces interpretation of the LIST as a multivalued
	       list, even if there is only a single scalar in the list.)
	       Example:

		   $shell = '/bin/csh';
		   exec $shell '-sh';	       # pretend it's a login shell

	       or, more directly,

		   exec {'/bin/csh'} '-sh';    # pretend it's a login shell

	       When the arguments get executed via the system shell, results
	       will be subject to its quirks and capabilities.	See "`STRING`"
	       in perlop for details.

	       Using an indirect object with "exec" or "system" is also more
	       secure.	This usage (which also works fine with system())
	       forces interpretation of the arguments as a multivalued list,
	       even if the list had just one argument.	That way you're safe
	       from the shell expanding wildcards or splitting up words with
	       whitespace in them.

		   @args = ( "echo surprise" );

		   exec @args;		     # subject to shell escapes
					       # if @args == 1
		   exec { $args[0] } @args;  # safe even with one-arg list

	       The first version, the one without the indirect object, ran the
	       echo program, passing it "surprise" an argument.	 The second
	       version didn't--it tried to run a program literally called
	       "echo surprise", didn't find it, and set $? to a non-zero value
	       indicating failure.

	       Beginning with v5.6.0, Perl will attempt to flush all files
	       opened for output before the exec, but this may not be
	       supported on some platforms (see perlport).  To be safe, you
	       may need to set $| ($AUTOFLUSH in English) or call the
	       "autoflush()" method of "IO::Handle" on any open handles in
	       order to avoid lost output.

	       Note that "exec" will not call your "END" blocks, nor will it
	       call any "DESTROY" methods in your objects.

       exists EXPR
	       Given an expression that specifies a hash element or array
	       element, returns true if the specified element in the hash or
	       array has ever been initialized, even if the corresponding
	       value is undefined.

		   print "Exists\n"    if exists $hash{$key};
		   print "Defined\n"   if defined $hash{$key};
		   print "True\n"      if $hash{$key};

		   print "Exists\n"    if exists $array[$index];
		   print "Defined\n"   if defined $array[$index];
		   print "True\n"      if $array[$index];

	       A hash or array element can be true only if it's defined, and
	       defined if it exists, but the reverse doesn't necessarily hold
	       true.

	       Given an expression that specifies the name of a subroutine,
	       returns true if the specified subroutine has ever been
	       declared, even if it is undefined.  Mentioning a subroutine
	       name for exists or defined does not count as declaring it.
	       Note that a subroutine which does not exist may still be
	       callable: its package may have an "AUTOLOAD" method that makes
	       it spring into existence the first time that it is called --
	       see perlsub.

		   print "Exists\n"    if exists &subroutine;
		   print "Defined\n"   if defined &subroutine;

	       Note that the EXPR can be arbitrarily complicated as long as
	       the final operation is a hash or array key lookup or subroutine
	       name:

		   if (exists $ref->{A}->{B}->{$key})  { }
		   if (exists $hash{A}{B}{$key})       { }

		   if (exists $ref->{A}->{B}->[$ix])   { }
		   if (exists $hash{A}{B}[$ix])	       { }

		   if (exists &{$ref->{A}{B}{$key}})   { }

	       Although the deepest nested array or hash will not spring into
	       existence just because its existence was tested, any
	       intervening ones will.  Thus "$ref->{"A"}" and
	       "$ref->{"A"}->{"B"}" will spring into existence due to the
	       existence test for the $key element above.  This happens
	       anywhere the arrow operator is used, including even:

		   undef $ref;
		   if (exists $ref->{"Some key"})      { }
		   print $ref;		   # prints HASH(0x80d3d5c)

	       This surprising autovivification in what does not at first--or
	       even second--glance appear to be an lvalue context may be fixed
	       in a future release.

	       Use of a subroutine call, rather than a subroutine name, as an
	       argument to exists() is an error.

		   exists ⊂	       # OK
		   exists &sub();      # Error

       exit EXPR
       exit    Evaluates EXPR and exits immediately with that value.
	       Example:

		   $ans = <STDIN>;
		   exit 0 if $ans =~ /^[Xx]/;

	       See also "die".	If EXPR is omitted, exits with 0 status.  The
	       only universally recognized values for EXPR are 0 for success
	       and 1 for error; other values are subject to interpretation
	       depending on the environment in which the Perl program is
	       running.	 For example, exiting 69 (EX_UNAVAILABLE) from a
	       sendmail incoming-mail filter will cause the mailer to return
	       the item undelivered, but that's not true everywhere.

	       Don't use "exit" to abort a subroutine if there's any chance
	       that someone might want to trap whatever error happened.	 Use
	       "die" instead, which can be trapped by an "eval".

	       The exit() function does not always exit immediately.  It calls
	       any defined "END" routines first, but these "END" routines may
	       not themselves abort the exit.  Likewise any object destructors
	       that need to be called are called before the real exit.	If
	       this is a problem, you can call "POSIX:_exit($status)" to avoid
	       END and destructor processing.  See perlmod for details.

       exp EXPR
       exp     Returns e (the natural logarithm base) to the power of EXPR.
	       If EXPR is omitted, gives "exp($_)".

       fcntl FILEHANDLE,FUNCTION,SCALAR
	       Implements the fcntl(2) function.  You'll probably have to say

		   use Fcntl;

	       first to get the correct constant definitions.  Argument
	       processing and value return works just like "ioctl" below.  For
	       example:

		   use Fcntl;
		   fcntl($filehandle, F_GETFL, $packed_return_buffer)
		       or die "can't fcntl F_GETFL: $!";

	       You don't have to check for "defined" on the return from
	       "fcntl".	 Like "ioctl", it maps a 0 return from the system call
	       into "0 but true" in Perl.  This string is true in boolean
	       context and 0 in numeric context.  It is also exempt from the
	       normal -w warnings on improper numeric conversions.

	       Note that "fcntl" will produce a fatal error if used on a
	       machine that doesn't implement fcntl(2).	 See the Fcntl module
	       or your fcntl(2) manpage to learn what functions are available
	       on your system.

	       Here's an example of setting a filehandle named "REMOTE" to be
	       non-blocking at the system level.  You'll have to negotiate $|
	       on your own, though.

		   use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);

		   $flags = fcntl(REMOTE, F_GETFL, 0)
			       or die "Can't get flags for the socket: $!\n";

		   $flags = fcntl(REMOTE, F_SETFL, $flags | O_NONBLOCK)
			       or die "Can't set flags for the socket: $!\n";

       fileno FILEHANDLE
	       Returns the file descriptor for a filehandle, or undefined if
	       the filehandle is not open.  This is mainly useful for
	       constructing bitmaps for "select" and low-level POSIX tty-
	       handling operations.  If FILEHANDLE is an expression, the value
	       is taken as an indirect filehandle, generally its name.

	       You can use this to find out whether two handles refer to the
	       same underlying descriptor:

		   if (fileno(THIS) == fileno(THAT)) {
		       print "THIS and THAT are dups\n";
		   }

	       (Filehandles connected to memory objects via new features of
	       "open" may return undefined even though they are open.)

       flock FILEHANDLE,OPERATION
	       Calls flock(2), or an emulation of it, on FILEHANDLE.  Returns
	       true for success, false on failure.  Produces a fatal error if
	       used on a machine that doesn't implement flock(2), fcntl(2)
	       locking, or lockf(3).  "flock" is Perl's portable file locking
	       interface, although it locks only entire files, not records.

	       Two potentially non-obvious but traditional "flock" semantics
	       are that it waits indefinitely until the lock is granted, and
	       that its locks merely advisory.	Such discretionary locks are
	       more flexible, but offer fewer guarantees.  This means that
	       programs that do not also use "flock" may modify files locked
	       with "flock".  See perlport, your port's specific
	       documentation, or your system-specific local manpages for
	       details.	 It's best to assume traditional behavior if you're
	       writing portable programs.  (But if you're not, you should as
	       always feel perfectly free to write for your own system's
	       idiosyncrasies (sometimes called "features").  Slavish
	       adherence to portability concerns shouldn't get in the way of
	       your getting your job done.)

	       OPERATION is one of LOCK_SH, LOCK_EX, or LOCK_UN, possibly
	       combined with LOCK_NB.  These constants are traditionally
	       valued 1, 2, 8 and 4, but you can use the symbolic names if you
	       import them from the Fcntl module, either individually, or as a
	       group using the ':flock' tag.  LOCK_SH requests a shared lock,
	       LOCK_EX requests an exclusive lock, and LOCK_UN releases a
	       previously requested lock.  If LOCK_NB is bitwise-or'ed with
	       LOCK_SH or LOCK_EX then "flock" will return immediately rather
	       than blocking waiting for the lock (check the return status to
	       see if you got it).

	       To avoid the possibility of miscoordination, Perl now flushes
	       FILEHANDLE before locking or unlocking it.

	       Note that the emulation built with lockf(3) doesn't provide
	       shared locks, and it requires that FILEHANDLE be open with
	       write intent.  These are the semantics that lockf(3)
	       implements.  Most if not all systems implement lockf(3) in
	       terms of fcntl(2) locking, though, so the differing semantics
	       shouldn't bite too many people.

	       Note that the fcntl(2) emulation of flock(3) requires that
	       FILEHANDLE be open with read intent to use LOCK_SH and requires
	       that it be open with write intent to use LOCK_EX.

	       Note also that some versions of "flock" cannot lock things over
	       the network; you would need to use the more system-specific
	       "fcntl" for that.  If you like you can force Perl to ignore
	       your system's flock(2) function, and so provide its own
	       fcntl(2)-based emulation, by passing the switch "-Ud_flock" to
	       the Configure program when you configure perl.

	       Here's a mailbox appender for BSD systems.

		   use Fcntl qw(:flock SEEK_END); # import LOCK_* and SEEK_END constants

		   sub lock {
		       my ($fh) = @_;
		       flock($fh, LOCK_EX) or die "Cannot lock mailbox - $!\n";

		       # and, in case someone appended while we were waiting...
		       seek($fh, 0, SEEK_END) or die "Cannot seek - $!\n";
		   }

		   sub unlock {
		       my ($fh) = @_;
		       flock($fh, LOCK_UN) or die "Cannot unlock mailbox - $!\n";
		   }

		   open(my $mbox, ">>", "/usr/spool/mail/$ENV{'USER'}")
			   or die "Can't open mailbox: $!";

		   lock($mbox);
		   print $mbox $msg,"\n\n";
		   unlock($mbox);

	       On systems that support a real flock(), locks are inherited
	       across fork() calls, whereas those that must resort to the more
	       capricious fcntl() function lose the locks, making it harder to
	       write servers.

	       See also DB_File for other flock() examples.

       fork    Does a fork(2) system call to create a new process running the
	       same program at the same point.	It returns the child pid to
	       the parent process, 0 to the child process, or "undef" if the
	       fork is unsuccessful.  File descriptors (and sometimes locks on
	       those descriptors) are shared, while everything else is copied.
	       On most systems supporting fork(), great care has gone into
	       making it extremely efficient (for example, using copy-on-write
	       technology on data pages), making it the dominant paradigm for
	       multitasking over the last few decades.

	       Beginning with v5.6.0, Perl will attempt to flush all files
	       opened for output before forking the child process, but this
	       may not be supported on some platforms (see perlport).  To be
	       safe, you may need to set $| ($AUTOFLUSH in English) or call
	       the "autoflush()" method of "IO::Handle" on any open handles in
	       order to avoid duplicate output.

	       If you "fork" without ever waiting on your children, you will
	       accumulate zombies.  On some systems, you can avoid this by
	       setting $SIG{CHLD} to "IGNORE".	See also perlipc for more
	       examples of forking and reaping moribund children.

	       Note that if your forked child inherits system file descriptors
	       like STDIN and STDOUT that are actually connected by a pipe or
	       socket, even if you exit, then the remote server (such as, say,
	       a CGI script or a backgrounded job launched from a remote
	       shell) won't think you're done.	You should reopen those to
	       /dev/null if it's any issue.

       format  Declare a picture format for use by the "write" function.  For
	       example:

		   format Something =
		       Test: @<<<<<<<< @||||| @>>>>>
			     $str,     $%,    '$' . int($num)
		   .

		   $str = "widget";
		   $num = $cost/$quantity;
		   $~ = 'Something';
		   write;

	       See perlform for many details and examples.

       formline PICTURE,LIST
	       This is an internal function used by "format"s, though you may
	       call it, too.  It formats (see perlform) a list of values
	       according to the contents of PICTURE, placing the output into
	       the format output accumulator, $^A (or $ACCUMULATOR in
	       English).  Eventually, when a "write" is done, the contents of
	       $^A are written to some filehandle.  You could also read $^A
	       and then set $^A back to "".  Note that a format typically does
	       one "formline" per line of form, but the "formline" function
	       itself doesn't care how many newlines are embedded in the
	       PICTURE.	 This means that the "~" and "~~" tokens will treat
	       the entire PICTURE as a single line.  You may therefore need to
	       use multiple formlines to implement a single record format,
	       just like the format compiler.

	       Be careful if you put double quotes around the picture, because
	       an "@" character may be taken to mean the beginning of an array
	       name.  "formline" always returns true.  See perlform for other
	       examples.

       getc FILEHANDLE
       getc    Returns the next character from the input file attached to
	       FILEHANDLE, or the undefined value at end of file, or if there
	       was an error (in the latter case $! is set).  If FILEHANDLE is
	       omitted, reads from STDIN.  This is not particularly efficient.
	       However, it cannot be used by itself to fetch single characters
	       without waiting for the user to hit enter.  For that, try
	       something more like:

		   if ($BSD_STYLE) {
		       system "stty cbreak </dev/tty >/dev/tty 2>&1";
		   }
		   else {
		       system "stty", '-icanon', 'eol', "\001";
		   }

		   $key = getc(STDIN);

		   if ($BSD_STYLE) {
		       system "stty -cbreak </dev/tty >/dev/tty 2>&1";
		   }
		   else {
		       system "stty", 'icanon', 'eol', '^@'; # ASCII null
		   }
		   print "\n";

	       Determination of whether $BSD_STYLE should be set is left as an
	       exercise to the reader.

	       The "POSIX::getattr" function can do this more portably on
	       systems purporting POSIX compliance.  See also the
	       "Term::ReadKey" module from your nearest CPAN site; details on
	       CPAN can be found on "CPAN" in perlmodlib.

       getlogin
	       This implements the C library function of the same name, which
	       on most systems returns the current login from /etc/utmp, if
	       any.  If null, use "getpwuid".

		   $login = getlogin || getpwuid($<) || "Kilroy";

	       Do not consider "getlogin" for authentication: it is not as
	       secure as "getpwuid".

       getpeername SOCKET
	       Returns the packed sockaddr address of other end of the SOCKET
	       connection.

		   use Socket;
		   $hersockaddr	   = getpeername(SOCK);
		   ($port, $iaddr) = sockaddr_in($hersockaddr);
		   $herhostname	   = gethostbyaddr($iaddr, AF_INET);
		   $herstraddr	   = inet_ntoa($iaddr);

       getpgrp PID
	       Returns the current process group for the specified PID.	 Use a
	       PID of 0 to get the current process group for the current
	       process.	 Will raise an exception if used on a machine that
	       doesn't implement getpgrp(2).  If PID is omitted, returns
	       process group of current process.  Note that the POSIX version
	       of "getpgrp" does not accept a PID argument, so only "PID==0"
	       is truly portable.

       getppid Returns the process id of the parent process.

	       Note for Linux users: on Linux, the C functions "getpid()" and
	       "getppid()" return different values from different threads. In
	       order to be portable, this behavior is not reflected by the
	       perl-level function "getppid()", that returns a consistent
	       value across threads. If you want to call the underlying
	       "getppid()", you may use the CPAN module "Linux::Pid".

       getpriority WHICH,WHO
	       Returns the current priority for a process, a process group, or
	       a user.	(See getpriority(2).)  Will raise a fatal exception if
	       used on a machine that doesn't implement getpriority(2).

       getpwnam NAME
       getgrnam NAME
       gethostbyname NAME
       getnetbyname NAME
       getprotobyname NAME
       getpwuid UID
       getgrgid GID
       getservbyname NAME,PROTO
       gethostbyaddr ADDR,ADDRTYPE
       getnetbyaddr ADDR,ADDRTYPE
       getprotobynumber NUMBER
       getservbyport PORT,PROTO
       getpwent
       getgrent
       gethostent
       getnetent
       getprotoent
       getservent
       setpwent
       setgrent
       sethostent STAYOPEN
       setnetent STAYOPEN
       setprotoent STAYOPEN
       setservent STAYOPEN
       endpwent
       endgrent
       endhostent
       endnetent
       endprotoent
       endservent
	       These routines perform the same functions as their counterparts
	       in the system library.  In list context, the return values from
	       the various get routines are as follows:

		   ($name,$passwd,$uid,$gid,
		      $quota,$comment,$gcos,$dir,$shell,$expire) = getpw*
		   ($name,$passwd,$gid,$members) = getgr*
		   ($name,$aliases,$addrtype,$length,@addrs) = gethost*
		   ($name,$aliases,$addrtype,$net) = getnet*
		   ($name,$aliases,$proto) = getproto*
		   ($name,$aliases,$port,$proto) = getserv*

	       (If the entry doesn't exist you get a null list.)

	       The exact meaning of the $gcos field varies but it usually
	       contains the real name of the user (as opposed to the login
	       name) and other information pertaining to the user.  Beware,
	       however, that in many system users are able to change this
	       information and therefore it cannot be trusted and therefore
	       the $gcos is tainted (see perlsec).  The $passwd and $shell,
	       user's encrypted password and login shell, are also tainted,
	       because of the same reason.

	       In scalar context, you get the name, unless the function was a
	       lookup by name, in which case you get the other thing, whatever
	       it is.  (If the entry doesn't exist you get the undefined
	       value.)	For example:

		   $uid	  = getpwnam($name);
		   $name  = getpwuid($num);
		   $name  = getpwent();
		   $gid	  = getgrnam($name);
		   $name  = getgrgid($num);
		   $name  = getgrent();
		   #etc.

	       In getpw*() the fields $quota, $comment, and $expire are
	       special cases in the sense that in many systems they are
	       unsupported.  If the $quota is unsupported, it is an empty
	       scalar.	If it is supported, it usually encodes the disk quota.
	       If the $comment field is unsupported, it is an empty scalar.
	       If it is supported it usually encodes some administrative
	       comment about the user.	In some systems the $quota field may
	       be $change or $age, fields that have to do with password aging.
	       In some systems the $comment field may be $class.  The $expire
	       field, if present, encodes the expiration period of the account
	       or the password.	 For the availability and the exact meaning of
	       these fields in your system, please consult your getpwnam(3)
	       documentation and your pwd.h file.  You can also find out from
	       within Perl what your $quota and $comment fields mean and
	       whether you have the $expire field by using the "Config" module
	       and the values "d_pwquota", "d_pwage", "d_pwchange",
	       "d_pwcomment", and "d_pwexpire".	 Shadow password files are
	       only supported if your vendor has implemented them in the
	       intuitive fashion that calling the regular C library routines
	       gets the shadow versions if you're running under privilege or
	       if there exists the shadow(3) functions as found in System V
	       (this includes Solaris and Linux.)  Those systems that
	       implement a proprietary shadow password facility are unlikely
	       to be supported.

	       The $members value returned by getgr*() is a space separated
	       list of the login names of the members of the group.

	       For the gethost*() functions, if the "h_errno" variable is
	       supported in C, it will be returned to you via $? if the
	       function call fails.  The @addrs value returned by a successful
	       call is a list of the raw addresses returned by the
	       corresponding system library call.  In the Internet domain,
	       each address is four bytes long and you can unpack it by saying
	       something like:

		   ($a,$b,$c,$d) = unpack('W4',$addr[0]);

	       The Socket library makes this slightly easier:

		   use Socket;
		   $iaddr = inet_aton("127.1"); # or whatever address
		   $name  = gethostbyaddr($iaddr, AF_INET);

		   # or going the other way
		   $straddr = inet_ntoa($iaddr);

	       In the opposite way, to resolve a hostname to the IP address
	       you can write this:

		   use Socket;
		   $packed_ip = gethostbyname("www.perl.org");
		   if (defined $packed_ip) {
		       $ip_address = inet_ntoa($packed_ip);
		   }

	       Make sure <gethostbyname()> is called in SCALAR context and
	       that its return value is checked for definedness.

	       If you get tired of remembering which element of the return
	       list contains which return value, by-name interfaces are
	       provided in standard modules: "File::stat", "Net::hostent",
	       "Net::netent", "Net::protoent", "Net::servent", "Time::gmtime",
	       "Time::localtime", and "User::grent".  These override the
	       normal built-ins, supplying versions that return objects with
	       the appropriate names for each field.  For example:

		  use File::stat;
		  use User::pwent;
		  $is_his = (stat($filename)->uid == pwent($whoever)->uid);

	       Even though it looks like they're the same method calls (uid),
	       they aren't, because a "File::stat" object is different from a
	       "User::pwent" object.

       getsockname SOCKET
	       Returns the packed sockaddr address of this end of the SOCKET
	       connection, in case you don't know the address because you have
	       several different IPs that the connection might have come in
	       on.

		   use Socket;
		   $mysockaddr = getsockname(SOCK);
		   ($port, $myaddr) = sockaddr_in($mysockaddr);
		   printf "Connect to %s [%s]\n",
		      scalar gethostbyaddr($myaddr, AF_INET),
		      inet_ntoa($myaddr);

       getsockopt SOCKET,LEVEL,OPTNAME
	       Queries the option named OPTNAME associated with SOCKET at a
	       given LEVEL.  Options may exist at multiple protocol levels
	       depending on the socket type, but at least the uppermost socket
	       level SOL_SOCKET (defined in the "Socket" module) will exist.
	       To query options at another level the protocol number of the
	       appropriate protocol controlling the option should be supplied.
	       For example, to indicate that an option is to be interpreted by
	       the TCP protocol, LEVEL should be set to the protocol number of
	       TCP, which you can get using getprotobyname.

	       The call returns a packed string representing the requested
	       socket option, or "undef" if there is an error (the error
	       reason will be in $!). What exactly is in the packed string
	       depends in the LEVEL and OPTNAME, consult your system
	       documentation for details. A very common case however is that
	       the option is an integer, in which case the result will be a
	       packed integer which you can decode using unpack with the "i"
	       (or "I") format.

	       An example testing if Nagle's algorithm is turned on on a
	       socket:

		   use Socket qw(:all);

		   defined(my $tcp = getprotobyname("tcp"))
		       or die "Could not determine the protocol number for tcp";
		   # my $tcp = IPPROTO_TCP; # Alternative
		   my $packed = getsockopt($socket, $tcp, TCP_NODELAY)
		       or die "Could not query TCP_NODELAY socket option: $!";
		   my $nodelay = unpack("I", $packed);
		   print "Nagle's algorithm is turned ", $nodelay ? "off\n" : "on\n";

       glob EXPR
       glob    In list context, returns a (possibly empty) list of filename
	       expansions on the value of EXPR such as the standard Unix shell
	       /bin/csh would do. In scalar context, glob iterates through
	       such filename expansions, returning undef when the list is
	       exhausted. This is the internal function implementing the
	       "<*.c>" operator, but you can use it directly. If EXPR is
	       omitted, $_ is used.  The "<*.c>" operator is discussed in more
	       detail in "I/O Operators" in perlop.

	       Note that "glob" will split its arguments on whitespace,
	       treating each segment as separate pattern.  As such, "glob('*.c
	       *.h')" would match all files with a .c or .h extension.	The
	       expression "glob('.* *')" would match all files in the current
	       working directory.

	       Beginning with v5.6.0, this operator is implemented using the
	       standard "File::Glob" extension.	 See File::Glob for details,
	       including "bsd_glob" which does not treat whitespace as a
	       pattern separator.

       gmtime EXPR
       gmtime  Works just like localtime but the returned values are localized
	       for the standard Greenwich time zone.

	       Note: when called in list context, $isdst, the last value
	       returned by gmtime is always 0.	There is no Daylight Saving
	       Time in GMT.

	       See "gmtime" in perlport for portability concerns.

       goto LABEL
       goto EXPR
       goto &NAME
	       The "goto-LABEL" form finds the statement labeled with LABEL
	       and resumes execution there.  It may not be used to go into any
	       construct that requires initialization, such as a subroutine or
	       a "foreach" loop.  It also can't be used to go into a construct
	       that is optimized away, or to get out of a block or subroutine
	       given to "sort".	 It can be used to go almost anywhere else
	       within the dynamic scope, including out of subroutines, but
	       it's usually better to use some other construct such as "last"
	       or "die".  The author of Perl has never felt the need to use
	       this form of "goto" (in Perl, that is--C is another matter).
	       (The difference being that C does not offer named loops
	       combined with loop control.  Perl does, and this replaces most
	       structured uses of "goto" in other languages.)

	       The "goto-EXPR" form expects a label name, whose scope will be
	       resolved dynamically.  This allows for computed "goto"s per
	       FORTRAN, but isn't necessarily recommended if you're optimizing
	       for maintainability:

		   goto ("FOO", "BAR", "GLARCH")[$i];

	       The "goto-&NAME" form is quite different from the other forms
	       of "goto".  In fact, it isn't a goto in the normal sense at
	       all, and doesn't have the stigma associated with other gotos.
	       Instead, it exits the current subroutine (losing any changes
	       set by local()) and immediately calls in its place the named
	       subroutine using the current value of @_.  This is used by
	       "AUTOLOAD" subroutines that wish to load another subroutine and
	       then pretend that the other subroutine had been called in the
	       first place (except that any modifications to @_ in the current
	       subroutine are propagated to the other subroutine.)  After the
	       "goto", not even "caller" will be able to tell that this
	       routine was called first.

	       NAME needn't be the name of a subroutine; it can be a scalar
	       variable containing a code reference, or a block that evaluates
	       to a code reference.

       grep BLOCK LIST
       grep EXPR,LIST
	       This is similar in spirit to, but not the same as, grep(1) and
	       its relatives.  In particular, it is not limited to using
	       regular expressions.

	       Evaluates the BLOCK or EXPR for each element of LIST (locally
	       setting $_ to each element) and returns the list value
	       consisting of those elements for which the expression evaluated
	       to true.	 In scalar context, returns the number of times the
	       expression was true.

		   @foo = grep(!/^#/, @bar);	# weed out comments

	       or equivalently,

		   @foo = grep {!/^#/} @bar;	# weed out comments

	       Note that $_ is an alias to the list value, so it can be used
	       to modify the elements of the LIST.  While this is useful and
	       supported, it can cause bizarre results if the elements of LIST
	       are not variables.  Similarly, grep returns aliases into the
	       original list, much as a for loop's index variable aliases the
	       list elements.  That is, modifying an element of a list
	       returned by grep (for example, in a "foreach", "map" or another
	       "grep") actually modifies the element in the original list.
	       This is usually something to be avoided when writing clear
	       code.

	       If $_ is lexical in the scope where the "grep" appears (because
	       it has been declared with "my $_") then, in addition to being
	       locally aliased to the list elements, $_ keeps being lexical
	       inside the block; i.e. it can't be seen from the outside,
	       avoiding any potential side-effects.

	       See also "map" for a list composed of the results of the BLOCK
	       or EXPR.

       hex EXPR
       hex     Interprets EXPR as a hex string and returns the corresponding
	       value.  (To convert strings that might start with either 0,
	       "0x", or "0b", see "oct".)  If EXPR is omitted, uses $_.

		   print hex '0xAf'; # prints '175'
		   print hex 'aF';   # same

	       Hex strings may only represent integers.	 Strings that would
	       cause integer overflow trigger a warning.  Leading whitespace
	       is not stripped, unlike oct(). To present something as hex,
	       look into "printf", "sprintf", or "unpack".

       import LIST
	       There is no builtin "import" function.  It is just an ordinary
	       method (subroutine) defined (or inherited) by modules that wish
	       to export names to another module.  The "use" function calls
	       the "import" method for the package used.  See also "use",
	       perlmod, and Exporter.

       index STR,SUBSTR,POSITION
       index STR,SUBSTR
	       The index function searches for one string within another, but
	       without the wildcard-like behavior of a full regular-expression
	       pattern match.  It returns the position of the first occurrence
	       of SUBSTR in STR at or after POSITION.  If POSITION is omitted,
	       starts searching from the beginning of the string.  POSITION
	       before the beginning of the string or after its end is treated
	       as if it were the beginning or the end, respectively.  POSITION
	       and the return value are based at 0 (or whatever you've set the
	       $[ variable to--but don't do that).  If the substring is not
	       found, "index" returns one less than the base, ordinarily "-1".

       int EXPR
       int     Returns the integer portion of EXPR.  If EXPR is omitted, uses
	       $_.  You should not use this function for rounding: one because
	       it truncates towards 0, and two because machine representations
	       of floating point numbers can sometimes produce
	       counterintuitive results.  For example, "int(-6.725/0.025)"
	       produces -268 rather than the correct -269; that's because it's
	       really more like -268.99999999999994315658 instead.  Usually,
	       the "sprintf", "printf", or the "POSIX::floor" and
	       "POSIX::ceil" functions will serve you better than will int().

       ioctl FILEHANDLE,FUNCTION,SCALAR
	       Implements the ioctl(2) function.  You'll probably first have
	       to say

		   require "sys/ioctl.ph";     # probably in $Config{archlib}/sys/ioctl.ph

	       to get the correct function definitions.	 If sys/ioctl.ph
	       doesn't exist or doesn't have the correct definitions you'll
	       have to roll your own, based on your C header files such as
	       <sys/ioctl.h>.  (There is a Perl script called h2ph that comes
	       with the Perl kit that may help you in this, but it's
	       nontrivial.)  SCALAR will be read and/or written depending on
	       the FUNCTION--a pointer to the string value of SCALAR will be
	       passed as the third argument of the actual "ioctl" call.	 (If
	       SCALAR has no string value but does have a numeric value, that
	       value will be passed rather than a pointer to the string value.
	       To guarantee this to be true, add a 0 to the scalar before
	       using it.)  The "pack" and "unpack" functions may be needed to
	       manipulate the values of structures used by "ioctl".

	       The return value of "ioctl" (and "fcntl") is as follows:

		       if OS returns:	       then Perl returns:
			   -1			 undefined value
			    0		       string "0 but true"
		       anything else		   that number

	       Thus Perl returns true on success and false on failure, yet you
	       can still easily determine the actual value returned by the
	       operating system:

		   $retval = ioctl(...) || -1;
		   printf "System returned %d\n", $retval;

	       The special string "0 but true" is exempt from -w complaints
	       about improper numeric conversions.

       join EXPR,LIST
	       Joins the separate strings of LIST into a single string with
	       fields separated by the value of EXPR, and returns that new
	       string.	Example:

		   $rec = join(':', $login,$passwd,$uid,$gid,$gcos,$home,$shell);

	       Beware that unlike "split", "join" doesn't take a pattern as
	       its first argument.  Compare "split".

       keys HASH
	       Returns a list consisting of all the keys of the named hash.
	       (In scalar context, returns the number of keys.)

	       The keys are returned in an apparently random order.  The
	       actual random order is subject to change in future versions of
	       perl, but it is guaranteed to be the same order as either the
	       "values" or "each" function produces (given that the hash has
	       not been modified).  Since Perl 5.8.1 the ordering is different
	       even between different runs of Perl for security reasons (see
	       "Algorithmic Complexity Attacks" in perlsec).

	       As a side effect, calling keys() resets the HASH's internal
	       iterator (see "each").  In particular, calling keys() in void
	       context resets the iterator with no other overhead.

	       Here is yet another way to print your environment:

		   @keys = keys %ENV;
		   @values = values %ENV;
		   while (@keys) {
		       print pop(@keys), '=', pop(@values), "\n";
		   }

	       or how about sorted by key:

		   foreach $key (sort(keys %ENV)) {
		       print $key, '=', $ENV{$key}, "\n";
		   }

	       The returned values are copies of the original keys in the
	       hash, so modifying them will not affect the original hash.
	       Compare "values".

	       To sort a hash by value, you'll need to use a "sort" function.
	       Here's a descending numeric sort of a hash by its values:

		   foreach $key (sort { $hash{$b} <=> $hash{$a} } keys %hash) {
		       printf "%4d %s\n", $hash{$key}, $key;
		   }

	       As an lvalue "keys" allows you to increase the number of hash
	       buckets allocated for the given hash.  This can gain you a
	       measure of efficiency if you know the hash is going to get big.
	       (This is similar to pre-extending an array by assigning a
	       larger number to $#array.)  If you say

		   keys %hash = 200;

	       then %hash will have at least 200 buckets allocated for it--256
	       of them, in fact, since it rounds up to the next power of two.
	       These buckets will be retained even if you do "%hash = ()", use
	       "undef %hash" if you want to free the storage while %hash is
	       still in scope.	You can't shrink the number of buckets
	       allocated for the hash using "keys" in this way (but you
	       needn't worry about doing this by accident, as trying has no
	       effect).

	       See also "each", "values" and "sort".

       kill SIGNAL, LIST
	       Sends a signal to a list of processes.  Returns the number of
	       processes successfully signaled (which is not necessarily the
	       same as the number actually killed).

		   $cnt = kill 1, $child1, $child2;
		   kill 9, @goners;

	       If SIGNAL is zero, no signal is sent to the process, but the
	       kill(2) system call will check whether it's possible to send a
	       signal to it (that means, to be brief, that the process is
	       owned by the same user, or we are the super-user).  This is a
	       useful way to check that a child process is alive (even if only
	       as a zombie) and hasn't changed its UID.	 See perlport for
	       notes on the portability of this construct.

	       Unlike in the shell, if SIGNAL is negative, it kills process
	       groups instead of processes.  (On System V, a negative PROCESS
	       number will also kill process groups, but that's not portable.)
	       That means you usually want to use positive not negative
	       signals.	 You may also use a signal name in quotes.

	       See "Signals" in perlipc for more details.

       last LABEL
       last    The "last" command is like the "break" statement in C (as used
	       in loops); it immediately exits the loop in question.  If the
	       LABEL is omitted, the command refers to the innermost enclosing
	       loop.  The "continue" block, if any, is not executed:

		   LINE: while (<STDIN>) {
		       last LINE if /^$/;      # exit when done with header
		       #...
		   }

	       "last" cannot be used to exit a block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep() or map() operation.

	       Note that a block by itself is semantically identical to a loop
	       that executes once.  Thus "last" can be used to effect an early
	       exit out of such a block.

	       See also "continue" for an illustration of how "last", "next",
	       and "redo" work.

       lc EXPR
       lc      Returns a lowercased version of EXPR.  This is the internal
	       function implementing the "\L" escape in double-quoted strings.
	       Respects current LC_CTYPE locale if "use locale" in force.  See
	       perllocale and perlunicode for more details about locale and
	       Unicode support.

	       If EXPR is omitted, uses $_.

       lcfirst EXPR
       lcfirst Returns the value of EXPR with the first character lowercased.
	       This is the internal function implementing the "\l" escape in
	       double-quoted strings.  Respects current LC_CTYPE locale if
	       "use locale" in force.  See perllocale and perlunicode for more
	       details about locale and Unicode support.

	       If EXPR is omitted, uses $_.

       length EXPR
       length  Returns the length in characters of the value of EXPR.  If EXPR
	       is omitted, returns length of $_.  Note that this cannot be
	       used on an entire array or hash to find out how many elements
	       these have.  For that, use "scalar @array" and "scalar keys
	       %hash" respectively.

	       Note the characters: if the EXPR is in Unicode, you will get
	       the number of characters, not the number of bytes.  To get the
	       length of the internal string in bytes, use
	       "bytes::length(EXPR)", see bytes.  Note that the internal
	       encoding is variable, and the number of bytes usually
	       meaningless.  To get the number of bytes that the string would
	       have when encoded as UTF-8, use
	       "length(Encoding::encode_utf8(EXPR))".

       link OLDFILE,NEWFILE
	       Creates a new filename linked to the old filename.  Returns
	       true for success, false otherwise.

       listen SOCKET,QUEUESIZE
	       Does the same thing that the listen system call does.  Returns
	       true if it succeeded, false otherwise.  See the example in
	       "Sockets: Client/Server Communication" in perlipc.

       local EXPR
	       You really probably want to be using "my" instead, because
	       "local" isn't what most people think of as "local".  See
	       "Private Variables via my()" in perlsub for details.

	       A local modifies the listed variables to be local to the
	       enclosing block, file, or eval.	If more than one value is
	       listed, the list must be placed in parentheses.	See "Temporary
	       Values via local()" in perlsub for details, including issues
	       with tied arrays and hashes.

       localtime EXPR
       localtime
	       Converts a time as returned by the time function to a 9-element
	       list with the time analyzed for the local time zone.  Typically
	       used as follows:

		   #  0	   1	2     3	    4	 5     6     7	   8
		   ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
							       localtime(time);

	       All list elements are numeric, and come straight out of the C
	       `struct tm'.  $sec, $min, and $hour are the seconds, minutes,
	       and hours of the specified time.

	       $mday is the day of the month, and $mon is the month itself, in
	       the range 0..11 with 0 indicating January and 11 indicating
	       December.  This makes it easy to get a month name from a list:

		   my @abbr = qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec );
		   print "$abbr[$mon] $mday";
		   # $mon=9, $mday=18 gives "Oct 18"

	       $year is the number of years since 1900, not just the last two
	       digits of the year.  That is, $year is 123 in year 2023.	 The
	       proper way to get a complete 4-digit year is simply:

		   $year += 1900;

	       Otherwise you create non-Y2K-compliant programs--and you
	       wouldn't want to do that, would you?

	       To get the last two digits of the year (e.g., '01' in 2001) do:

		   $year = sprintf("%02d", $year % 100);

	       $wday is the day of the week, with 0 indicating Sunday and 3
	       indicating Wednesday.  $yday is the day of the year, in the
	       range 0..364 (or 0..365 in leap years.)

	       $isdst is true if the specified time occurs during Daylight
	       Saving Time, false otherwise.

	       If EXPR is omitted, "localtime()" uses the current time (as
	       returned by time(3)).

	       In scalar context, "localtime()" returns the ctime(3) value:

		   $now_string = localtime;  # e.g., "Thu Oct 13 04:54:34 1994"

	       This scalar value is not locale dependent but is a Perl
	       builtin. For GMT instead of local time use the "gmtime"
	       builtin. See also the "Time::Local" module (to convert the
	       second, minutes, hours, ... back to the integer value returned
	       by time()), and the POSIX module's strftime(3) and mktime(3)
	       functions.

	       To get somewhat similar but locale dependent date strings, set
	       up your locale environment variables appropriately (please see
	       perllocale) and try for example:

		   use POSIX qw(strftime);
		   $now_string = strftime "%a %b %e %H:%M:%S %Y", localtime;
		   # or for GMT formatted appropriately for your locale:
		   $now_string = strftime "%a %b %e %H:%M:%S %Y", gmtime;

	       Note that the %a and %b, the short forms of the day of the week
	       and the month of the year, may not necessarily be three
	       characters wide.

	       See "localtime" in perlport for portability concerns.

	       The Time::gmtime and Time::localtime modules provides a
	       convenient, by-name access mechanism to the gmtime() and
	       localtime() functions, respectively.

	       For a comprehensive date and time representation look at the
	       DateTime module on CPAN.

       lock THING
	       This function places an advisory lock on a shared variable, or
	       referenced object contained in THING until the lock goes out of
	       scope.

	       lock() is a "weak keyword" : this means that if you've defined
	       a function by this name (before any calls to it), that function
	       will be called instead. (However, if you've said "use threads",
	       lock() is always a keyword.) See threads.

       log EXPR
       log     Returns the natural logarithm (base e) of EXPR.	If EXPR is
	       omitted, returns log of $_.  To get the log of another base,
	       use basic algebra: The base-N log of a number is equal to the
	       natural log of that number divided by the natural log of N.
	       For example:

		   sub log10 {
		       my $n = shift;
		       return log($n)/log(10);
		   }

	       See also "exp" for the inverse operation.

       lstat EXPR
       lstat   Does the same thing as the "stat" function (including setting
	       the special "_" filehandle) but stats a symbolic link instead
	       of the file the symbolic link points to.	 If symbolic links are
	       unimplemented on your system, a normal "stat" is done.  For
	       much more detailed information, please see the documentation
	       for "stat".

	       If EXPR is omitted, stats $_.

       m//     The match operator.  See "Regexp Quote-Like Operators" in
	       perlop.

       map BLOCK LIST
       map EXPR,LIST
	       Evaluates the BLOCK or EXPR for each element of LIST (locally
	       setting $_ to each element) and returns the list value composed
	       of the results of each such evaluation.	In scalar context,
	       returns the total number of elements so generated.  Evaluates
	       BLOCK or EXPR in list context, so each element of LIST may
	       produce zero, one, or more elements in the returned value.

		   @chars = map(chr, @nums);

	       translates a list of numbers to the corresponding characters.
	       And

		   %hash = map { get_a_key_for($_) => $_ } @array;

	       is just a funny way to write

		   %hash = ();
		   foreach (@array) {
		       $hash{get_a_key_for($_)} = $_;
		   }

	       Note that $_ is an alias to the list value, so it can be used
	       to modify the elements of the LIST.  While this is useful and
	       supported, it can cause bizarre results if the elements of LIST
	       are not variables.  Using a regular "foreach" loop for this
	       purpose would be clearer in most cases.	See also "grep" for an
	       array composed of those items of the original list for which
	       the BLOCK or EXPR evaluates to true.

	       If $_ is lexical in the scope where the "map" appears (because
	       it has been declared with "my $_"), then, in addition to being
	       locally aliased to the list elements, $_ keeps being lexical
	       inside the block; that is, it can't be seen from the outside,
	       avoiding any potential side-effects.

	       "{" starts both hash references and blocks, so "map { ..."
	       could be either the start of map BLOCK LIST or map EXPR, LIST.
	       Because perl doesn't look ahead for the closing "}" it has to
	       take a guess at which its dealing with based what it finds just
	       after the "{". Usually it gets it right, but if it doesn't it
	       won't realize something is wrong until it gets to the "}" and
	       encounters the missing (or unexpected) comma. The syntax error
	       will be reported close to the "}" but you'll need to change
	       something near the "{" such as using a unary "+" to give perl
	       some help:

		   %hash = map {  "\L$_", 1  } @array  # perl guesses EXPR.  wrong
		   %hash = map { +"\L$_", 1  } @array  # perl guesses BLOCK. right
		   %hash = map { ("\L$_", 1) } @array  # this also works
		   %hash = map {  lc($_), 1  } @array  # as does this.
		   %hash = map +( lc($_), 1 ), @array  # this is EXPR and works!

		   %hash = map	( lc($_), 1 ), @array  # evaluates to (1, @array)

	       or to force an anon hash constructor use "+{":

		  @hashes = map +{ lc($_), 1 }, @array # EXPR, so needs , at end

	       and you get list of anonymous hashes each with only 1 entry.

       mkdir FILENAME,MASK
       mkdir FILENAME
       mkdir   Creates the directory specified by FILENAME, with permissions
	       specified by MASK (as modified by "umask").  If it succeeds it
	       returns true, otherwise it returns false and sets $! (errno).
	       If omitted, MASK defaults to 0777. If omitted, FILENAME
	       defaults to $_.

	       In general, it is better to create directories with permissive
	       MASK, and let the user modify that with their "umask", than it
	       is to supply a restrictive MASK and give the user no way to be
	       more permissive.	 The exceptions to this rule are when the file
	       or directory should be kept private (mail files, for instance).
	       The perlfunc(1) entry on "umask" discusses the choice of MASK
	       in more detail.

	       Note that according to the POSIX 1003.1-1996 the FILENAME may
	       have any number of trailing slashes.  Some operating and
	       filesystems do not get this right, so Perl automatically
	       removes all trailing slashes to keep everyone happy.

	       In order to recursively create a directory structure look at
	       the "mkpath" function of the File::Path module.

       msgctl ID,CMD,ARG
	       Calls the System V IPC function msgctl(2).  You'll probably
	       have to say

		   use IPC::SysV;

	       first to get the correct constant definitions.  If CMD is
	       "IPC_STAT", then ARG must be a variable that will hold the
	       returned "msqid_ds" structure.  Returns like "ioctl": the
	       undefined value for error, "0 but true" for zero, or the actual
	       return value otherwise.	See also "SysV IPC" in perlipc,
	       "IPC::SysV", and "IPC::Semaphore" documentation.

       msgget KEY,FLAGS
	       Calls the System V IPC function msgget(2).  Returns the message
	       queue id, or the undefined value if there is an error.  See
	       also "SysV IPC" in perlipc and "IPC::SysV" and "IPC::Msg"
	       documentation.

       msgrcv ID,VAR,SIZE,TYPE,FLAGS
	       Calls the System V IPC function msgrcv to receive a message
	       from message queue ID into variable VAR with a maximum message
	       size of SIZE.  Note that when a message is received, the
	       message type as a native long integer will be the first thing
	       in VAR, followed by the actual message.	This packing may be
	       opened with "unpack("l! a*")".  Taints the variable.  Returns
	       true if successful, or false if there is an error.  See also
	       "SysV IPC" in perlipc, "IPC::SysV", and "IPC::SysV::Msg"
	       documentation.

       msgsnd ID,MSG,FLAGS
	       Calls the System V IPC function msgsnd to send the message MSG
	       to the message queue ID.	 MSG must begin with the native long
	       integer message type, and be followed by the length of the
	       actual message, and finally the message itself.	This kind of
	       packing can be achieved with "pack("l! a*", $type, $message)".
	       Returns true if successful, or false if there is an error.  See
	       also "IPC::SysV" and "IPC::SysV::Msg" documentation.

       my EXPR
       my TYPE EXPR
       my EXPR : ATTRS
       my TYPE EXPR : ATTRS
	       A "my" declares the listed variables to be local (lexically) to
	       the enclosing block, file, or "eval".  If more than one value
	       is listed, the list must be placed in parentheses.

	       The exact semantics and interface of TYPE and ATTRS are still
	       evolving.  TYPE is currently bound to the use of "fields"
	       pragma, and attributes are handled using the "attributes"
	       pragma, or starting from Perl 5.8.0 also via the
	       "Attribute::Handlers" module.  See "Private Variables via my()"
	       in perlsub for details, and fields, attributes, and
	       Attribute::Handlers.

       next LABEL
       next    The "next" command is like the "continue" statement in C; it
	       starts the next iteration of the loop:

		   LINE: while (<STDIN>) {
		       next LINE if /^#/;      # discard comments
		       #...
		   }

	       Note that if there were a "continue" block on the above, it
	       would get executed even on discarded lines.  If the LABEL is
	       omitted, the command refers to the innermost enclosing loop.

	       "next" cannot be used to exit a block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep() or map() operation.

	       Note that a block by itself is semantically identical to a loop
	       that executes once.  Thus "next" will exit such a block early.

	       See also "continue" for an illustration of how "last", "next",
	       and "redo" work.

       no Module VERSION LIST
       no Module VERSION
       no Module LIST
       no Module
       no VERSION
	       See the "use" function, of which "no" is the opposite.

       oct EXPR
       oct     Interprets EXPR as an octal string and returns the
	       corresponding value.  (If EXPR happens to start off with "0x",
	       interprets it as a hex string.  If EXPR starts off with "0b",
	       it is interpreted as a binary string.  Leading whitespace is
	       ignored in all three cases.)  The following will handle
	       decimal, binary, octal, and hex in the standard Perl or C
	       notation:

		   $val = oct($val) if $val =~ /^0/;

	       If EXPR is omitted, uses $_.   To go the other way (produce a
	       number in octal), use sprintf() or printf():

		   $perms = (stat("filename"))[2] & 07777;
		   $oct_perms = sprintf "%lo", $perms;

	       The oct() function is commonly used when a string such as 644
	       needs to be converted into a file mode, for example. (Although
	       perl will automatically convert strings into numbers as needed,
	       this automatic conversion assumes base 10.)

       open FILEHANDLE,EXPR
       open FILEHANDLE,MODE,EXPR
       open FILEHANDLE,MODE,EXPR,LIST
       open FILEHANDLE,MODE,REFERENCE
       open FILEHANDLE
	       Opens the file whose filename is given by EXPR, and associates
	       it with FILEHANDLE.

	       Simple examples to open a file for reading:

		   open(my $fh, '<', "input.txt") or die $!;

	       and for writing:

		   open(my $fh, '>', "output.txt") or die $!;

	       (The following is a comprehensive reference to open(): for a
	       gentler introduction you may consider perlopentut.)

	       If FILEHANDLE is an undefined scalar variable (or array or hash
	       element) the variable is assigned a reference to a new
	       anonymous filehandle, otherwise if FILEHANDLE is an expression,
	       its value is used as the name of the real filehandle wanted.
	       (This is considered a symbolic reference, so "use strict
	       'refs'" should not be in effect.)

	       If EXPR is omitted, the scalar variable of the same name as the
	       FILEHANDLE contains the filename.  (Note that lexical
	       variables--those declared with "my"--will not work for this
	       purpose; so if you're using "my", specify EXPR in your call to
	       open.)

	       If three or more arguments are specified then the mode of
	       opening and the file name are separate. If MODE is '<' or
	       nothing, the file is opened for input.  If MODE is '>', the
	       file is truncated and opened for output, being created if
	       necessary.  If MODE is '>>', the file is opened for appending,
	       again being created if necessary.

	       You can put a '+' in front of the '>' or '<' to indicate that
	       you want both read and write access to the file; thus '+<' is
	       almost always preferred for read/write updates--the '+>' mode
	       would clobber the file first.  You can't usually use either
	       read-write mode for updating textfiles, since they have
	       variable length records.	 See the -i switch in perlrun for a
	       better approach.	 The file is created with permissions of 0666
	       modified by the process' "umask" value.

	       These various prefixes correspond to the fopen(3) modes of 'r',
	       'r+', 'w', 'w+', 'a', and 'a+'.

	       In the 2-arguments (and 1-argument) form of the call the mode
	       and filename should be concatenated (in this order), possibly
	       separated by spaces.  It is possible to omit the mode in these
	       forms if the mode is '<'.

	       If the filename begins with '|', the filename is interpreted as
	       a command to which output is to be piped, and if the filename
	       ends with a '|', the filename is interpreted as a command which
	       pipes output to us.  See "Using open() for IPC" in perlipc for
	       more examples of this.  (You are not allowed to "open" to a
	       command that pipes both in and out, but see IPC::Open2,
	       IPC::Open3, and "Bidirectional Communication with Another
	       Process" in perlipc for alternatives.)

	       For three or more arguments if MODE is '|-', the filename is
	       interpreted as a command to which output is to be piped, and if
	       MODE is '-|', the filename is interpreted as a command which
	       pipes output to us.  In the 2-arguments (and 1-argument) form
	       one should replace dash ('-') with the command.	See "Using
	       open() for IPC" in perlipc for more examples of this.  (You are
	       not allowed to "open" to a command that pipes both in and out,
	       but see IPC::Open2, IPC::Open3, and "Bidirectional
	       Communication" in perlipc for alternatives.)

	       In the three-or-more argument form of pipe opens, if LIST is
	       specified (extra arguments after the command name) then LIST
	       becomes arguments to the command invoked if the platform
	       supports it.  The meaning of "open" with more than three
	       arguments for non-pipe modes is not yet specified. Experimental
	       "layers" may give extra LIST arguments meaning.

	       In the 2-arguments (and 1-argument) form opening '-' opens
	       STDIN and opening '>-' opens STDOUT.

	       You may use the three-argument form of open to specify IO
	       "layers" (sometimes also referred to as "disciplines") to be
	       applied to the handle that affect how the input and output are
	       processed (see open and PerlIO for more details). For example

		 open(my $fh, "<:encoding(UTF-8)", "file")

	       will open the UTF-8 encoded file containing Unicode characters,
	       see perluniintro. Note that if layers are specified in the
	       three-arg form then default layers stored in ${^OPEN} (see
	       perlvar; usually set by the open pragma or the switch -CioD)
	       are ignored.

	       Open returns nonzero upon success, the undefined value
	       otherwise.  If the "open" involved a pipe, the return value
	       happens to be the pid of the subprocess.

	       If you're running Perl on a system that distinguishes between
	       text files and binary files, then you should check out
	       "binmode" for tips for dealing with this.  The key distinction
	       between systems that need "binmode" and those that don't is
	       their text file formats.	 Systems like Unix, Mac OS, and Plan
	       9, which delimit lines with a single character, and which
	       encode that character in C as "\n", do not need "binmode".  The
	       rest need it.

	       When opening a file, it's usually a bad idea to continue normal
	       execution if the request failed, so "open" is frequently used
	       in connection with "die".  Even if "die" won't do what you want
	       (say, in a CGI script, where you want to make a nicely
	       formatted error message (but there are modules that can help
	       with that problem)) you should always check the return value
	       from opening a file.  The infrequent exception is when working
	       with an unopened filehandle is actually what you want to do.

	       As a special case the 3-arg form with a read/write mode and the
	       third argument being "undef":

		   open(my $tmp, "+>", undef) or die ...

	       opens a filehandle to an anonymous temporary file.  Also using
	       "+<" works for symmetry, but you really should consider writing
	       something to the temporary file first.  You will need to seek()
	       to do the reading.

	       Since v5.8.0, perl has built using PerlIO by default.  Unless
	       you've changed this (i.e. Configure -Uuseperlio), you can open
	       file handles to "in memory" files held in Perl scalars via:

		   open($fh, '>', \$variable) || ..

	       Though if you try to re-open "STDOUT" or "STDERR" as an "in
	       memory" file, you have to close it first:

		   close STDOUT;
		   open STDOUT, '>', \$variable or die "Can't open STDOUT: $!";

	       Examples:

		   $ARTICLE = 100;
		   open ARTICLE or die "Can't find article $ARTICLE: $!\n";
		   while (<ARTICLE>) {...

		   open(LOG, '>>/usr/spool/news/twitlog');     # (log is reserved)
		   # if the open fails, output is discarded

		   open(my $dbase, '+<', 'dbase.mine')	       # open for update
		       or die "Can't open 'dbase.mine' for update: $!";

		   open(my $dbase, '+<dbase.mine')		       # ditto
		       or die "Can't open 'dbase.mine' for update: $!";

		   open(ARTICLE, '-|', "caesar <$article")     # decrypt article
		       or die "Can't start caesar: $!";

		   open(ARTICLE, "caesar <$article |")	       # ditto
		       or die "Can't start caesar: $!";

		   open(EXTRACT, "|sort >Tmp$$")	       # $$ is our process id
		       or die "Can't start sort: $!";

		   # in memory files
		   open(MEMORY,'>', \$var)
		       or die "Can't open memory file: $!";
		   print MEMORY "foo!\n";		       # output will end up in $var

		   # process argument list of files along with any includes

		   foreach $file (@ARGV) {
		       process($file, 'fh00');
		   }

		   sub process {
		       my($filename, $input) = @_;
		       $input++;	       # this is a string increment
		       unless (open($input, $filename)) {
			   print STDERR "Can't open $filename: $!\n";
			   return;
		       }

		       local $_;
		       while (<$input>) {	       # note use of indirection
			   if (/^#include "(.*)"/) {
			       process($1, $input);
			       next;
			   }
			   #...		       # whatever
		       }
		   }

	       See perliol for detailed info on PerlIO.

	       You may also, in the Bourne shell tradition, specify an EXPR
	       beginning with '>&', in which case the rest of the string is
	       interpreted as the name of a filehandle (or file descriptor, if
	       numeric) to be duped (as dup(2)) and opened.  You may use "&"
	       after ">", ">>", "<", "+>", "+>>", and "+<".  The mode you
	       specify should match the mode of the original filehandle.
	       (Duping a filehandle does not take into account any existing
	       contents of IO buffers.) If you use the 3-arg form then you can
	       pass either a number, the name of a filehandle or the normal
	       "reference to a glob".

	       Here is a script that saves, redirects, and restores "STDOUT"
	       and "STDERR" using various methods:

		   #!/usr/bin/perl
		   open my $oldout, ">&STDOUT"	   or die "Can't dup STDOUT: $!";
		   open OLDERR,	    ">&", \*STDERR or die "Can't dup STDERR: $!";

		   open STDOUT, '>', "foo.out" or die "Can't redirect STDOUT: $!";
		   open STDERR, ">&STDOUT"     or die "Can't dup STDOUT: $!";

		   select STDERR; $| = 1;      # make unbuffered
		   select STDOUT; $| = 1;      # make unbuffered

		   print STDOUT "stdout 1\n";  # this works for
		   print STDERR "stderr 1\n";  # subprocesses too

		   open STDOUT, ">&", $oldout or die "Can't dup \$oldout: $!";
		   open STDERR, ">&OLDERR"    or die "Can't dup OLDERR: $!";

		   print STDOUT "stdout 2\n";
		   print STDERR "stderr 2\n";

	       If you specify '<&=X', where "X" is a file descriptor number or
	       a filehandle, then Perl will do an equivalent of C's "fdopen"
	       of that file descriptor (and not call dup(2)); this is more
	       parsimonious of file descriptors.  For example:

		   # open for input, reusing the fileno of $fd
		   open(FILEHANDLE, "<&=$fd")

	       or

		   open(FILEHANDLE, "<&=", $fd)

	       or

		   # open for append, using the fileno of OLDFH
		   open(FH, ">>&=", OLDFH)

	       or

		   open(FH, ">>&=OLDFH")

	       Being parsimonious on filehandles is also useful (besides being
	       parsimonious) for example when something is dependent on file
	       descriptors, like for example locking using flock().  If you do
	       just "open(A, '>>&B')", the filehandle A will not have the same
	       file descriptor as B, and therefore flock(A) will not flock(B),
	       and vice versa.	But with "open(A, '>>&=B')" the filehandles
	       will share the same file descriptor.

	       Note that if you are using Perls older than 5.8.0, Perl will be
	       using the standard C libraries' fdopen() to implement the "="
	       functionality.  On many UNIX systems fdopen() fails when file
	       descriptors exceed a certain value, typically 255.  For Perls
	       5.8.0 and later, PerlIO is most often the default.

	       You can see whether Perl has been compiled with PerlIO or not
	       by running "perl -V" and looking for "useperlio=" line.	If
	       "useperlio" is "define", you have PerlIO, otherwise you don't.

	       If you open a pipe on the command '-', i.e., either '|-' or
	       '-|' with 2-arguments (or 1-argument) form of open(), then
	       there is an implicit fork done, and the return value of open is
	       the pid of the child within the parent process, and 0 within
	       the child process.  (Use "defined($pid)" to determine whether
	       the open was successful.)  The filehandle behaves normally for
	       the parent, but i/o to that filehandle is piped from/to the
	       STDOUT/STDIN of the child process.  In the child process the
	       filehandle isn't opened--i/o happens from/to the new STDOUT or
	       STDIN.  Typically this is used like the normal piped open when
	       you want to exercise more control over just how the pipe
	       command gets executed, such as when you are running setuid, and
	       don't want to have to scan shell commands for metacharacters.
	       The following triples are more or less equivalent:

		   open(FOO, "|tr '[a-z]' '[A-Z]'");
		   open(FOO, '|-', "tr '[a-z]' '[A-Z]'");
		   open(FOO, '|-') || exec 'tr', '[a-z]', '[A-Z]';
		   open(FOO, '|-', "tr", '[a-z]', '[A-Z]');

		   open(FOO, "cat -n '$file'|");
		   open(FOO, '-|', "cat -n '$file'");
		   open(FOO, '-|') || exec 'cat', '-n', $file;
		   open(FOO, '-|', "cat", '-n', $file);

	       The last example in each block shows the pipe as "list form",
	       which is not yet supported on all platforms.  A good rule of
	       thumb is that if your platform has true "fork()" (in other
	       words, if your platform is UNIX) you can use the list form.

	       See "Safe Pipe Opens" in perlipc for more examples of this.

	       Beginning with v5.6.0, Perl will attempt to flush all files
	       opened for output before any operation that may do a fork, but
	       this may not be supported on some platforms (see perlport).  To
	       be safe, you may need to set $| ($AUTOFLUSH in English) or call
	       the "autoflush()" method of "IO::Handle" on any open handles.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened file descriptor as determined
	       by the value of $^F.  See "$^F" in perlvar.

	       Closing any piped filehandle causes the parent process to wait
	       for the child to finish, and returns the status value in $? and
	       "${^CHILD_ERROR_NATIVE}".

	       The filename passed to 2-argument (or 1-argument) form of
	       open() will have leading and trailing whitespace deleted, and
	       the normal redirection characters honored.  This property,
	       known as "magic open", can often be used to good effect.	 A
	       user could specify a filename of "rsh cat file |", or you could
	       change certain filenames as needed:

		   $filename =~ s/(.*\.gz)\s*$/gzip -dc < $1|/;
		   open(FH, $filename) or die "Can't open $filename: $!";

	       Use 3-argument form to open a file with arbitrary weird
	       characters in it,

		   open(FOO, '<', $file);

	       otherwise it's necessary to protect any leading and trailing
	       whitespace:

		   $file =~ s#^(\s)#./$1#;
		   open(FOO, "< $file\0");

	       (this may not work on some bizarre filesystems).	 One should
	       conscientiously choose between the magic and 3-arguments form
	       of open():

		   open IN, $ARGV[0];

	       will allow the user to specify an argument of the form "rsh cat
	       file |", but will not work on a filename which happens to have
	       a trailing space, while

		   open IN, '<', $ARGV[0];

	       will have exactly the opposite restrictions.

	       If you want a "real" C "open" (see open(2) on your system),
	       then you should use the "sysopen" function, which involves no
	       such magic (but may use subtly different filemodes than Perl
	       open(), which is mapped to C fopen()).  This is another way to
	       protect your filenames from interpretation.  For example:

		   use IO::Handle;
		   sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)
		       or die "sysopen $path: $!";
		   $oldfh = select(HANDLE); $| = 1; select($oldfh);
		   print HANDLE "stuff $$\n";
		   seek(HANDLE, 0, 0);
		   print "File contains: ", <HANDLE>;

	       Using the constructor from the "IO::Handle" package (or one of
	       its subclasses, such as "IO::File" or "IO::Socket"), you can
	       generate anonymous filehandles that have the scope of whatever
	       variables hold references to them, and automatically close
	       whenever and however you leave that scope:

		   use IO::File;
		   #...
		   sub read_myfile_munged {
		       my $ALL = shift;
		       my $handle = IO::File->new;
		       open($handle, "myfile") or die "myfile: $!";
		       $first = <$handle>
			   or return ();     # Automatically closed here.
		       mung $first or die "mung failed";       # Or here.
		       return $first, <$handle> if $ALL;       # Or here.
		       $first;				       # Or here.
		   }

	       See "seek" for some details about mixing reading and writing.

       opendir DIRHANDLE,EXPR
	       Opens a directory named EXPR for processing by "readdir",
	       "telldir", "seekdir", "rewinddir", and "closedir".  Returns
	       true if successful.  DIRHANDLE may be an expression whose value
	       can be used as an indirect dirhandle, usually the real
	       dirhandle name.	If DIRHANDLE is an undefined scalar variable
	       (or array or hash element), the variable is assigned a
	       reference to a new anonymous dirhandle.	DIRHANDLEs have their
	       own namespace separate from FILEHANDLEs.

	       See example at "readdir".

       ord EXPR
       ord     Returns the numeric (the native 8-bit encoding, like ASCII or
	       EBCDIC, or Unicode) value of the first character of EXPR.  If
	       EXPR is omitted, uses $_.

	       For the reverse, see "chr".  See perlunicode for more about
	       Unicode.

       our EXPR
       our TYPE EXPR
       our EXPR : ATTRS
       our TYPE EXPR : ATTRS
	       "our" associates a simple name with a package variable in the
	       current package for use within the current scope.  When "use
	       strict 'vars'" is in effect, "our" lets you use declared global
	       variables without qualifying them with package names, within
	       the lexical scope of the "our" declaration.  In this way "our"
	       differs from "use vars", which is package scoped.

	       Unlike "my", which both allocates storage for a variable and
	       associates a simple name with that storage for use within the
	       current scope, "our" associates a simple name with a package
	       variable in the current package, for use within the current
	       scope.  In other words, "our" has the same scoping rules as
	       "my", but does not necessarily create a variable.

	       If more than one value is listed, the list must be placed in
	       parentheses.

		   our $foo;
		   our($bar, $baz);

	       An "our" declaration declares a global variable that will be
	       visible across its entire lexical scope, even across package
	       boundaries.  The package in which the variable is entered is
	       determined at the point of the declaration, not at the point of
	       use.  This means the following behavior holds:

		   package Foo;
		   our $bar;	       # declares $Foo::bar for rest of lexical scope
		   $bar = 20;

		   package Bar;
		   print $bar;	       # prints 20, as it refers to $Foo::bar

	       Multiple "our" declarations with the same name in the same
	       lexical scope are allowed if they are in different packages.
	       If they happen to be in the same package, Perl will emit
	       warnings if you have asked for them, just like multiple "my"
	       declarations.  Unlike a second "my" declaration, which will
	       bind the name to a fresh variable, a second "our" declaration
	       in the same package, in the same scope, is merely redundant.

		   use warnings;
		   package Foo;
		   our $bar;	       # declares $Foo::bar for rest of lexical scope
		   $bar = 20;

		   package Bar;
		   our $bar = 30;      # declares $Bar::bar for rest of lexical scope
		   print $bar;	       # prints 30

		   our $bar;	       # emits warning but has no other effect
		   print $bar;	       # still prints 30

	       An "our" declaration may also have a list of attributes
	       associated with it.

	       The exact semantics and interface of TYPE and ATTRS are still
	       evolving.  TYPE is currently bound to the use of "fields"
	       pragma, and attributes are handled using the "attributes"
	       pragma, or starting from Perl 5.8.0 also via the
	       "Attribute::Handlers" module.  See "Private Variables via my()"
	       in perlsub for details, and fields, attributes, and
	       Attribute::Handlers.

       pack TEMPLATE,LIST
	       Takes a LIST of values and converts it into a string using the
	       rules given by the TEMPLATE.  The resulting string is the
	       concatenation of the converted values.  Typically, each
	       converted value looks like its machine-level representation.
	       For example, on 32-bit machines an integer may be represented
	       by a sequence of 4 bytes that will be converted to a sequence
	       of 4 characters.

	       The TEMPLATE is a sequence of characters that give the order
	       and type of values, as follows:

		   a   A string with arbitrary binary data, will be null padded.
		   A   A text (ASCII) string, will be space padded.
		   Z   A null terminated (ASCIZ) string, will be null padded.

		   b   A bit string (ascending bit order inside each byte, like vec()).
		   B   A bit string (descending bit order inside each byte).
		   h   A hex string (low nybble first).
		   H   A hex string (high nybble first).

		   c   A signed char (8-bit) value.
		   C   An unsigned char (octet) value.
		   W   An unsigned char value (can be greater than 255).

		   s   A signed short (16-bit) value.
		   S   An unsigned short value.

		   l   A signed long (32-bit) value.
		   L   An unsigned long value.

		   q   A signed quad (64-bit) value.
		   Q   An unsigned quad value.
			 (Quads are available only if your system supports 64-bit
			  integer values _and_ if Perl has been compiled to support those.
			  Causes a fatal error otherwise.)

		   i   A signed integer value.
		   I   A unsigned integer value.
			 (This 'integer' is _at_least_ 32 bits wide.  Its exact
			  size depends on what a local C compiler calls 'int'.)

		   n   An unsigned short (16-bit) in "network" (big-endian) order.
		   N   An unsigned long (32-bit) in "network" (big-endian) order.
		   v   An unsigned short (16-bit) in "VAX" (little-endian) order.
		   V   An unsigned long (32-bit) in "VAX" (little-endian) order.

		   j   A Perl internal signed integer value (IV).
		   J   A Perl internal unsigned integer value (UV).

		   f   A single-precision float in the native format.
		   d   A double-precision float in the native format.

		   F   A Perl internal floating point value (NV) in the native format
		   D   A long double-precision float in the native format.
			 (Long doubles are available only if your system supports long
			  double values _and_ if Perl has been compiled to support those.
			  Causes a fatal error otherwise.)

		   p   A pointer to a null-terminated string.
		   P   A pointer to a structure (fixed-length string).

		   u   A uuencoded string.
		   U   A Unicode character number.  Encodes to a character in character mode
		       and UTF-8 (or UTF-EBCDIC in EBCDIC platforms) in byte mode.

		   w   A BER compressed integer (not an ASN.1 BER, see perlpacktut for
		       details).  Its bytes represent an unsigned integer in base 128,
		       most significant digit first, with as few digits as possible.  Bit
		       eight (the high bit) is set on each byte except the last.

		   x   A null byte.
		   X   Back up a byte.
		   @   Null fill or truncate to absolute position, counted from the
		       start of the innermost ()-group.
		   .   Null fill or truncate to absolute position specified by value.
		   (   Start of a ()-group.

	       One or more of the modifiers below may optionally follow some
	       letters in the TEMPLATE (the second column lists the letters
	       for which the modifier is valid):

		   !   sSlLiI	  Forces native (short, long, int) sizes instead
				  of fixed (16-/32-bit) sizes.

		       xX	  Make x and X act as alignment commands.

		       nNvV	  Treat integers as signed instead of unsigned.

		       @.	  Specify position as byte offset in the internal
				  representation of the packed string. Efficient but
				  dangerous.

		   >   sSiIlLqQ	  Force big-endian byte-order on the type.
		       jJfFdDpP	  (The "big end" touches the construct.)

		   <   sSiIlLqQ	  Force little-endian byte-order on the type.
		       jJfFdDpP	  (The "little end" touches the construct.)

	       The ">" and "<" modifiers can also be used on "()"-groups, in
	       which case they force a certain byte-order on all components of
	       that group, including subgroups.

	       The following rules apply:

	       ·       Each letter may optionally be followed by a number
		       giving a repeat count.  With all types except "a", "A",
		       "Z", "b", "B", "h", "H", "@", ".", "x", "X" and "P" the
		       pack function will gobble up that many values from the
		       LIST.  A "*" for the repeat count means to use however
		       many items are left, except for "@", "x", "X", where it
		       is equivalent to 0, for <.> where it means relative to
		       string start and "u", where it is equivalent to 1 (or
		       45, which is the same).	A numeric repeat count may
		       optionally be enclosed in brackets, as in "pack
		       'C[80]', @arr".

		       One can replace the numeric repeat count by a template
		       enclosed in brackets; then the packed length of this
		       template in bytes is used as a count.  For example,
		       "x[L]" skips a long (it skips the number of bytes in a
		       long); the template "$t X[$t] $t" unpack()s twice what
		       $t unpacks.  If the template in brackets contains
		       alignment commands (such as "x![d]"), its packed length
		       is calculated as if the start of the template has the
		       maximal possible alignment.

		       When used with "Z", "*" results in the addition of a
		       trailing null byte (so the packed result will be one
		       longer than the byte "length" of the item).

		       When used with "@", the repeat count represents an
		       offset from the start of the innermost () group.

		       When used with ".", the repeat count is used to
		       determine the starting position from where the value
		       offset is calculated. If the repeat count is 0, it's
		       relative to the current position. If the repeat count
		       is "*", the offset is relative to the start of the
		       packed string. And if its an integer "n" the offset is
		       relative to the start of the n-th innermost () group
		       (or the start of the string if "n" is bigger then the
		       group level).

		       The repeat count for "u" is interpreted as the maximal
		       number of bytes to encode per line of output, with 0, 1
		       and 2 replaced by 45. The repeat count should not be
		       more than 65.

	       ·       The "a", "A", and "Z" types gobble just one value, but
		       pack it as a string of length count, padding with nulls
		       or spaces as necessary.	When unpacking, "A" strips
		       trailing whitespace and nulls, "Z" strips everything
		       after the first null, and "a" returns data verbatim.

		       If the value-to-pack is too long, it is truncated.  If
		       too long and an explicit count is provided, "Z" packs
		       only "$count-1" bytes, followed by a null byte.	Thus
		       "Z" always packs a trailing null (except when the count
		       is 0).

	       ·       Likewise, the "b" and "B" fields pack a string that
		       many bits long.	Each character of the input field of
		       pack() generates 1 bit of the result.  Each result bit
		       is based on the least-significant bit of the
		       corresponding input character, i.e., on "ord($char)%2".
		       In particular, characters "0" and "1" generate bits 0
		       and 1, as do characters "\0" and "\1".

		       Starting from the beginning of the input string of
		       pack(), each 8-tuple of characters is converted to 1
		       character of output.  With format "b" the first
		       character of the 8-tuple determines the least-
		       significant bit of a character, and with format "B" it
		       determines the most-significant bit of a character.

		       If the length of the input string is not exactly
		       divisible by 8, the remainder is packed as if the input
		       string were padded by null characters at the end.
		       Similarly, during unpack()ing the "extra" bits are
		       ignored.

		       If the input string of pack() is longer than needed,
		       extra characters are ignored. A "*" for the repeat
		       count of pack() means to use all the characters of the
		       input field.  On unpack()ing the bits are converted to
		       a string of "0"s and "1"s.

	       ·       The "h" and "H" fields pack a string that many nybbles
		       (4-bit groups, representable as hexadecimal digits,
		       0-9a-f) long.

		       Each character of the input field of pack() generates 4
		       bits of the result.  For non-alphabetical characters
		       the result is based on the 4 least-significant bits of
		       the input character, i.e., on "ord($char)%16".  In
		       particular, characters "0" and "1" generate nybbles 0
		       and 1, as do bytes "\0" and "\1".  For characters
		       "a".."f" and "A".."F" the result is compatible with the
		       usual hexadecimal digits, so that "a" and "A" both
		       generate the nybble "0xa==10".  The result for
		       characters "g".."z" and "G".."Z" is not well-defined.

		       Starting from the beginning of the input string of
		       pack(), each pair of characters is converted to 1
		       character of output.  With format "h" the first
		       character of the pair determines the least-significant
		       nybble of the output character, and with format "H" it
		       determines the most-significant nybble.

		       If the length of the input string is not even, it
		       behaves as if padded by a null character at the end.
		       Similarly, during unpack()ing the "extra" nybbles are
		       ignored.

		       If the input string of pack() is longer than needed,
		       extra characters are ignored.  A "*" for the repeat
		       count of pack() means to use all the characters of the
		       input field.  On unpack()ing the nybbles are converted
		       to a string of hexadecimal digits.

	       ·       The "p" type packs a pointer to a null-terminated
		       string.	You are responsible for ensuring the string is
		       not a temporary value (which can potentially get
		       deallocated before you get around to using the packed
		       result).	 The "P" type packs a pointer to a structure
		       of the size indicated by the length.  A NULL pointer is
		       created if the corresponding value for "p" or "P" is
		       "undef", similarly for unpack().

		       If your system has a strange pointer size (i.e. a
		       pointer is neither as big as an int nor as big as a
		       long), it may not be possible to pack or unpack
		       pointers in big- or little-endian byte order.
		       Attempting to do so will result in a fatal error.

	       ·       The "/" template character allows packing and unpacking
		       of a sequence of items where the packed structure
		       contains a packed item count followed by the packed
		       items themselves.

		       For "pack" you write length-item"/"sequence-item and
		       the length-item describes how the length value is
		       packed. The ones likely to be of most use are integer-
		       packing ones like "n" (for Java strings), "w" (for
		       ASN.1 or SNMP) and "N" (for Sun XDR).

		       For "pack", the sequence-item may have a repeat count,
		       in which case the minimum of that and the number of
		       available items is used as argument for the length-
		       item. If it has no repeat count or uses a '*', the
		       number of available items is used.

		       For "unpack" an internal stack of integer arguments
		       unpacked so far is used. You write "/"sequence-item and
		       the repeat count is obtained by popping off the last
		       element from the stack. The sequence-item must not have
		       a repeat count.

		       If the sequence-item refers to a string type ("A", "a"
		       or "Z"), the length-item is a string length, not a
		       number of strings. If there is an explicit repeat count
		       for pack, the packed string will be adjusted to that
		       given length.

			   unpack 'W/a', "\04Gurusamy";		   gives ('Guru')
			   unpack 'a3/A A*', '007 Bond	J ';	   gives (' Bond', 'J')
			   unpack 'a3 x2 /A A*', '007: Bond, J.';  gives ('Bond, J', '.')
			   pack 'n/a* w/a','hello,','world';	   gives "\000\006hello,\005world"
			   pack 'a/W2', ord('a') .. ord('z');	   gives '2ab'

		       The length-item is not returned explicitly from
		       "unpack".

		       Adding a count to the length-item letter is unlikely to
		       do anything useful, unless that letter is "A", "a" or
		       "Z".  Packing with a length-item of "a" or "Z" may
		       introduce "\000" characters, which Perl does not regard
		       as legal in numeric strings.

	       ·       The integer types "s", "S", "l", and "L" may be
		       followed by a "!" modifier to signify native shorts or
		       longs--as you can see from above for example a bare "l"
		       does mean exactly 32 bits, the native "long" (as seen
		       by the local C compiler) may be larger.	This is an
		       issue mainly in 64-bit platforms.  You can see whether
		       using "!" makes any difference by

			       print length(pack("s")), " ", length(pack("s!")), "\n";
			       print length(pack("l")), " ", length(pack("l!")), "\n";

		       "i!" and "I!" also work but only because of
		       completeness; they are identical to "i" and "I".

		       The actual sizes (in bytes) of native shorts, ints,
		       longs, and long longs on the platform where Perl was
		       built are also available via Config:

			      use Config;
			      print $Config{shortsize},	   "\n";
			      print $Config{intsize},	   "\n";
			      print $Config{longsize},	   "\n";
			      print $Config{longlongsize}, "\n";

		       (The $Config{longlongsize} will be undefined if your
		       system does not support long longs.)

	       ·       The integer formats "s", "S", "i", "I", "l", "L", "j",
		       and "J" are inherently non-portable between processors
		       and operating systems because they obey the native
		       byteorder and endianness.  For example a 4-byte integer
		       0x12345678 (305419896 decimal) would be ordered
		       natively (arranged in and handled by the CPU registers)
		       into bytes as

			       0x12 0x34 0x56 0x78     # big-endian
			       0x78 0x56 0x34 0x12     # little-endian

		       Basically, the Intel and VAX CPUs are little-endian,
		       while everybody else, for example Motorola m68k/88k,
		       PPC, Sparc, HP PA, Power, and Cray are big-endian.
		       Alpha and MIPS can be either: Digital/Compaq used/uses
		       them in little-endian mode; SGI/Cray uses them in big-
		       endian mode.

		       The names `big-endian' and `little-endian' are comic
		       references to the classic "Gulliver's Travels" (via the
		       paper "On Holy Wars and a Plea for Peace" by Danny
		       Cohen, USC/ISI IEN 137, April 1, 1980) and the egg-
		       eating habits of the Lilliputians.

		       Some systems may have even weirder byte orders such as

			       0x56 0x78 0x12 0x34
			       0x34 0x12 0x78 0x56

		       You can see your system's preference with

			       print join(" ", map { sprintf "%#02x", $_ }
						   unpack("W*",pack("L",0x12345678))), "\n";

		       The byteorder on the platform where Perl was built is
		       also available via Config:

			       use Config;
			       print $Config{byteorder}, "\n";

		       Byteorders '1234' and '12345678' are little-endian,
		       '4321' and '87654321' are big-endian.

		       If you want portable packed integers you can either use
		       the formats "n", "N", "v", and "V", or you can use the
		       ">" and "<" modifiers.  These modifiers are only
		       available as of perl 5.9.2.  See also perlport.

	       ·       All integer and floating point formats as well as "p"
		       and "P" and "()"-groups may be followed by the ">" or
		       "<" modifiers to force big- or little- endian byte-
		       order, respectively.  This is especially useful, since
		       "n", "N", "v" and "V" don't cover signed integers,
		       64-bit integers and floating point values.  However,
		       there are some things to keep in mind.

		       Exchanging signed integers between different platforms
		       only works if all platforms store them in the same
		       format.	Most platforms store signed integers in two's
		       complement, so usually this is not an issue.

		       The ">" or "<" modifiers can only be used on floating
		       point formats on big- or little-endian machines.
		       Otherwise, attempting to do so will result in a fatal
		       error.

		       Forcing big- or little-endian byte-order on floating
		       point values for data exchange can only work if all
		       platforms are using the same binary representation
		       (e.g. IEEE floating point format).  Even if all
		       platforms are using IEEE, there may be subtle
		       differences.  Being able to use ">" or "<" on floating
		       point values can be very useful, but also very
		       dangerous if you don't know exactly what you're doing.
		       It is definitely not a general way to portably store
		       floating point values.

		       When using ">" or "<" on an "()"-group, this will
		       affect all types inside the group that accept the byte-
		       order modifiers, including all subgroups.  It will
		       silently be ignored for all other types.	 You are not
		       allowed to override the byte-order within a group that
		       already has a byte-order modifier suffix.

	       ·       Real numbers (floats and doubles) are in the native
		       machine format only; due to the multiplicity of
		       floating formats around, and the lack of a standard
		       "network" representation, no facility for interchange
		       has been made.  This means that packed floating point
		       data written on one machine may not be readable on
		       another - even if both use IEEE floating point
		       arithmetic (as the endian-ness of the memory
		       representation is not part of the IEEE spec).  See also
		       perlport.

		       If you know exactly what you're doing, you can use the
		       ">" or "<" modifiers to force big- or little-endian
		       byte-order on floating point values.

		       Note that Perl uses doubles (or long doubles, if
		       configured) internally for all numeric calculation, and
		       converting from double into float and thence back to
		       double again will lose precision (i.e., "unpack("f",
		       pack("f", $foo)") will not in general equal $foo).

	       ·       Pack and unpack can operate in two modes, character
		       mode ("C0" mode) where the packed string is processed
		       per character and UTF-8 mode ("U0" mode) where the
		       packed string is processed in its UTF-8-encoded Unicode
		       form on a byte by byte basis. Character mode is the
		       default unless the format string starts with an "U".
		       You can switch mode at any moment with an explicit "C0"
		       or "U0" in the format. A mode is in effect until the
		       next mode switch or until the end of the ()-group in
		       which it was entered.

	       ·       You must yourself do any alignment or padding by
		       inserting for example enough 'x'es while packing.
		       There is no way to pack() and unpack() could know where
		       the characters are going to or coming from.  Therefore
		       "pack" (and "unpack") handle their output and input as
		       flat sequences of characters.

	       ·       A ()-group is a sub-TEMPLATE enclosed in parentheses.
		       A group may take a repeat count, both as postfix, and
		       for unpack() also via the "/" template character.
		       Within each repetition of a group, positioning with "@"
		       starts again at 0. Therefore, the result of

			   pack( '@1A((@2A)@3A)', 'a', 'b', 'c' )

		       is the string "\0a\0\0bc".

	       ·       "x" and "X" accept "!" modifier.	 In this case they act
		       as alignment commands: they jump forward/back to the
		       closest position aligned at a multiple of "count"
		       characters. For example, to pack() or unpack() C's
		       "struct {char c; double d; char cc[2]}" one may need to
		       use the template "W x![d] d W[2]"; this assumes that
		       doubles must be aligned on the double's size.

		       For alignment commands "count" of 0 is equivalent to
		       "count" of 1; both result in no-ops.

	       ·       "n", "N", "v" and "V" accept the "!" modifier. In this
		       case they will represent signed 16-/32-bit integers in
		       big-/little-endian order.  This is only portable if all
		       platforms sharing the packed data use the same binary
		       representation for signed integers (e.g. all platforms
		       are using two's complement representation).

	       ·       A comment in a TEMPLATE starts with "#" and goes to the
		       end of line.  White space may be used to separate pack
		       codes from each other, but modifiers and a repeat count
		       must follow immediately.

	       ·       If TEMPLATE requires more arguments to pack() than
		       actually given, pack() assumes additional "" arguments.
		       If TEMPLATE requires fewer arguments to pack() than
		       actually given, extra arguments are ignored.

	       Examples:

		   $foo = pack("WWWW",65,66,67,68);
		   # foo eq "ABCD"
		   $foo = pack("W4",65,66,67,68);
		   # same thing
		   $foo = pack("W4",0x24b6,0x24b7,0x24b8,0x24b9);
		   # same thing with Unicode circled letters.
		   $foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);
		   # same thing with Unicode circled letters. You don't get the UTF-8
		   # bytes because the U at the start of the format caused a switch to
		   # U0-mode, so the UTF-8 bytes get joined into characters
		   $foo = pack("C0U4",0x24b6,0x24b7,0x24b8,0x24b9);
		   # foo eq "\xe2\x92\xb6\xe2\x92\xb7\xe2\x92\xb8\xe2\x92\xb9"
		   # This is the UTF-8 encoding of the string in the previous example

		   $foo = pack("ccxxcc",65,66,67,68);
		   # foo eq "AB\0\0CD"

		   # note: the above examples featuring "W" and "c" are true
		   # only on ASCII and ASCII-derived systems such as ISO Latin 1
		   # and UTF-8.	 In EBCDIC the first example would be
		   # $foo = pack("WWWW",193,194,195,196);

		   $foo = pack("s2",1,2);
		   # "\1\0\2\0" on little-endian
		   # "\0\1\0\2" on big-endian

		   $foo = pack("a4","abcd","x","y","z");
		   # "abcd"

		   $foo = pack("aaaa","abcd","x","y","z");
		   # "axyz"

		   $foo = pack("a14","abcdefg");
		   # "abcdefg\0\0\0\0\0\0\0"

		   $foo = pack("i9pl", gmtime);
		   # a real struct tm (on my system anyway)

		   $utmp_template = "Z8 Z8 Z16 L";
		   $utmp = pack($utmp_template, @utmp1);
		   # a struct utmp (BSDish)

		   @utmp2 = unpack($utmp_template, $utmp);
		   # "@utmp1" eq "@utmp2"

		   sub bintodec {
		       unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
		   }

		   $foo = pack('sx2l', 12, 34);
		   # short 12, two zero bytes padding, long 34
		   $bar = pack('s@4l', 12, 34);
		   # short 12, zero fill to position 4, long 34
		   # $foo eq $bar
		   $baz = pack('s.l', 12, 4, 34);
		   # short 12, zero fill to position 4, long 34

		   $foo = pack('nN', 42, 4711);
		   # pack big-endian 16- and 32-bit unsigned integers
		   $foo = pack('S>L>', 42, 4711);
		   # exactly the same
		   $foo = pack('s<l<', -42, 4711);
		   # pack little-endian 16- and 32-bit signed integers
		   $foo = pack('(sl)<', -42, 4711);
		   # exactly the same

	       The same template may generally also be used in unpack().

       package NAMESPACE
       package Declares the compilation unit as being in the given namespace.
	       The scope of the package declaration is from the declaration
	       itself through the end of the enclosing block, file, or eval
	       (the same as the "my" operator).	 All further unqualified
	       dynamic identifiers will be in this namespace.  A package
	       statement affects only dynamic variables--including those
	       you've used "local" on--but not lexical variables, which are
	       created with "my".  Typically it would be the first declaration
	       in a file to be included by the "require" or "use" operator.
	       You can switch into a package in more than one place; it merely
	       influences which symbol table is used by the compiler for the
	       rest of that block.  You can refer to variables and filehandles
	       in other packages by prefixing the identifier with the package
	       name and a double colon:	 $Package::Variable.  If the package
	       name is null, the "main" package as assumed.  That is, $::sail
	       is equivalent to $main::sail (as well as to "$main'sail", still
	       seen in older code).

	       See "Packages" in perlmod for more information about packages,
	       modules, and classes.  See perlsub for other scoping issues.

       pipe READHANDLE,WRITEHANDLE
	       Opens a pair of connected pipes like the corresponding system
	       call.  Note that if you set up a loop of piped processes,
	       deadlock can occur unless you are very careful.	In addition,
	       note that Perl's pipes use IO buffering, so you may need to set
	       $| to flush your WRITEHANDLE after each command, depending on
	       the application.

	       See IPC::Open2, IPC::Open3, and "Bidirectional Communication"
	       in perlipc for examples of such things.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened file descriptors as determined
	       by the value of $^F.  See "$^F" in perlvar.

       pop ARRAY
       pop     Pops and returns the last value of the array, shortening the
	       array by one element.

	       If there are no elements in the array, returns the undefined
	       value (although this may happen at other times as well).	 If
	       ARRAY is omitted, pops the @ARGV array in the main program, and
	       the @_ array in subroutines, just like "shift".

       pos SCALAR
       pos     Returns the offset of where the last "m//g" search left off for
	       the variable in question ($_ is used when the variable is not
	       specified).  Note that 0 is a valid match offset.  "undef"
	       indicates that the search position is reset (usually due to
	       match failure, but can also be because no match has yet been
	       performed on the scalar). "pos" directly accesses the location
	       used by the regexp engine to store the offset, so assigning to
	       "pos" will change that offset, and so will also influence the
	       "\G" zero-width assertion in regular expressions. Because a
	       failed "m//gc" match doesn't reset the offset, the return from
	       "pos" won't change either in this case.	See perlre and perlop.

       print FILEHANDLE LIST
       print LIST
       print   Prints a string or a list of strings.  Returns true if
	       successful.  FILEHANDLE may be a scalar variable name, in which
	       case the variable contains the name of or a reference to the
	       filehandle, thus introducing one level of indirection.  (NOTE:
	       If FILEHANDLE is a variable and the next token is a term, it
	       may be misinterpreted as an operator unless you interpose a "+"
	       or put parentheses around the arguments.)  If FILEHANDLE is
	       omitted, prints by default to standard output (or to the last
	       selected output channel--see "select").	If LIST is also
	       omitted, prints $_ to the currently selected output channel.
	       To set the default output channel to something other than
	       STDOUT use the select operation.	 The current value of $, (if
	       any) is printed between each LIST item.	The current value of
	       "$\" (if any) is printed after the entire LIST has been
	       printed.	 Because print takes a LIST, anything in the LIST is
	       evaluated in list context, and any subroutine that you call
	       will have one or more of its expressions evaluated in list
	       context.	 Also be careful not to follow the print keyword with
	       a left parenthesis unless you want the corresponding right
	       parenthesis to terminate the arguments to the print--interpose
	       a "+" or put parentheses around all the arguments.

	       Note that if you're storing FILEHANDLEs in an array, or if
	       you're using any other expression more complex than a scalar
	       variable to retrieve it, you will have to use a block returning
	       the filehandle value instead:

		   print { $files[$i] } "stuff\n";
		   print { $OK ? STDOUT : STDERR } "stuff\n";

       printf FILEHANDLE FORMAT, LIST
       printf FORMAT, LIST
	       Equivalent to "print FILEHANDLE sprintf(FORMAT, LIST)", except
	       that "$\" (the output record separator) is not appended.	 The
	       first argument of the list will be interpreted as the "printf"
	       format. See "sprintf" for an explanation of the format
	       argument.  If "use locale" is in effect, and POSIX::setlocale()
	       has been called, the character used for the decimal separator
	       in formatted floating point numbers is affected by the
	       LC_NUMERIC locale.  See perllocale and POSIX.

	       Don't fall into the trap of using a "printf" when a simple
	       "print" would do.  The "print" is more efficient and less error
	       prone.

       prototype FUNCTION
	       Returns the prototype of a function as a string (or "undef" if
	       the function has no prototype).	FUNCTION is a reference to, or
	       the name of, the function whose prototype you want to retrieve.

	       If FUNCTION is a string starting with "CORE::", the rest is
	       taken as a name for Perl builtin.  If the builtin is not
	       overridable (such as "qw//") or if its arguments cannot be
	       adequately expressed by a prototype (such as "system"),
	       prototype() returns "undef", because the builtin does not
	       really behave like a Perl function.  Otherwise, the string
	       describing the equivalent prototype is returned.

       push ARRAY,LIST
	       Treats ARRAY as a stack, and pushes the values of LIST onto the
	       end of ARRAY.  The length of ARRAY increases by the length of
	       LIST.  Has the same effect as

		   for $value (LIST) {
		       $ARRAY[++$#ARRAY] = $value;
		   }

	       but is more efficient.  Returns the number of elements in the
	       array following the completed "push".

       q/STRING/
       qq/STRING/
       qx/STRING/
       qw/STRING/
	       Generalized quotes.  See "Quote-Like Operators" in perlop.

       qr/STRING/
	       Regexp-like quote.  See "Regexp Quote-Like Operators" in
	       perlop.

       quotemeta EXPR
       quotemeta
	       Returns the value of EXPR with all non-"word" characters
	       backslashed.  (That is, all characters not matching
	       "/[A-Za-z_0-9]/" will be preceded by a backslash in the
	       returned string, regardless of any locale settings.)  This is
	       the internal function implementing the "\Q" escape in double-
	       quoted strings.

	       If EXPR is omitted, uses $_.

       rand EXPR
       rand    Returns a random fractional number greater than or equal to 0
	       and less than the value of EXPR.	 (EXPR should be positive.)
	       If EXPR is omitted, the value 1 is used.	 Currently EXPR with
	       the value 0 is also special-cased as 1 - this has not been
	       documented before perl 5.8.0 and is subject to change in future
	       versions of perl.  Automatically calls "srand" unless "srand"
	       has already been called.	 See also "srand".

	       Apply "int()" to the value returned by "rand()" if you want
	       random integers instead of random fractional numbers.  For
	       example,

		   int(rand(10))

	       returns a random integer between 0 and 9, inclusive.

	       (Note: If your rand function consistently returns numbers that
	       are too large or too small, then your version of Perl was
	       probably compiled with the wrong number of RANDBITS.)

       read FILEHANDLE,SCALAR,LENGTH,OFFSET
       read FILEHANDLE,SCALAR,LENGTH
	       Attempts to read LENGTH characters of data into variable SCALAR
	       from the specified FILEHANDLE.  Returns the number of
	       characters actually read, 0 at end of file, or undef if there
	       was an error (in the latter case $! is also set).  SCALAR will
	       be grown or shrunk so that the last character actually read is
	       the last character of the scalar after the read.

	       An OFFSET may be specified to place the read data at some place
	       in the string other than the beginning.	A negative OFFSET
	       specifies placement at that many characters counting backwards
	       from the end of the string.  A positive OFFSET greater than the
	       length of SCALAR results in the string being padded to the
	       required size with "\0" bytes before the result of the read is
	       appended.

	       The call is actually implemented in terms of either Perl's or
	       system's fread() call.  To get a true read(2) system call, see
	       "sysread".

	       Note the characters: depending on the status of the filehandle,
	       either (8-bit) bytes or characters are read.  By default all
	       filehandles operate on bytes, but for example if the filehandle
	       has been opened with the ":utf8" I/O layer (see "open", and the
	       "open" pragma, open), the I/O will operate on UTF-8 encoded
	       Unicode characters, not bytes.  Similarly for the ":encoding"
	       pragma: in that case pretty much any characters can be read.

       readdir DIRHANDLE
	       Returns the next directory entry for a directory opened by
	       "opendir".  If used in list context, returns all the rest of
	       the entries in the directory.  If there are no more entries,
	       returns an undefined value in scalar context or a null list in
	       list context.

	       If you're planning to filetest the return values out of a
	       "readdir", you'd better prepend the directory in question.
	       Otherwise, because we didn't "chdir" there, it would have been
	       testing the wrong file.

		   opendir(my $dh, $some_dir) || die "can't opendir $some_dir: $!";
		   @dots = grep { /^\./ && -f "$some_dir/$_" } readdir($dh);
		   closedir $dh;

       readline EXPR
       readline
	       Reads from the filehandle whose typeglob is contained in EXPR
	       (or from *ARGV if EXPR is not provided).	 In scalar context,
	       each call reads and returns the next line, until end-of-file is
	       reached, whereupon the subsequent call returns undef.  In list
	       context, reads until end-of-file is reached and returns a list
	       of lines.  Note that the notion of "line" used here is however
	       you may have defined it with $/ or $INPUT_RECORD_SEPARATOR).
	       See "$/" in perlvar.

	       When $/ is set to "undef", when readline() is in scalar context
	       (i.e. file slurp mode), and when an empty file is read, it
	       returns '' the first time, followed by "undef" subsequently.

	       This is the internal function implementing the "<EXPR>"
	       operator, but you can use it directly.  The "<EXPR>" operator
	       is discussed in more detail in "I/O Operators" in perlop.

		   $line = <STDIN>;
		   $line = readline(*STDIN);	       # same thing

	       If readline encounters an operating system error, $! will be
	       set with the corresponding error message.  It can be helpful to
	       check $! when you are reading from filehandles you don't trust,
	       such as a tty or a socket.  The following example uses the
	       operator form of "readline", and takes the necessary steps to
	       ensure that "readline" was successful.

		   for (;;) {
		       undef $!;
		       unless (defined( $line = <> )) {
			   last if eof;
			   die $! if $!;
		       }
		       # ...
		   }

       readlink EXPR
       readlink
	       Returns the value of a symbolic link, if symbolic links are
	       implemented.  If not, gives a fatal error.  If there is some
	       system error, returns the undefined value and sets $! (errno).
	       If EXPR is omitted, uses $_.

       readpipe EXPR
       readpipe
	       EXPR is executed as a system command.  The collected standard
	       output of the command is returned.  In scalar context, it comes
	       back as a single (potentially multi-line) string.  In list
	       context, returns a list of lines (however you've defined lines
	       with $/ or $INPUT_RECORD_SEPARATOR).  This is the internal
	       function implementing the "qx/EXPR/" operator, but you can use
	       it directly.  The "qx/EXPR/" operator is discussed in more
	       detail in "I/O Operators" in perlop.  If EXPR is omitted, uses
	       $_.

       recv SOCKET,SCALAR,LENGTH,FLAGS
	       Receives a message on a socket.	Attempts to receive LENGTH
	       characters of data into variable SCALAR from the specified
	       SOCKET filehandle.  SCALAR will be grown or shrunk to the
	       length actually read.  Takes the same flags as the system call
	       of the same name.  Returns the address of the sender if
	       SOCKET's protocol supports this; returns an empty string
	       otherwise.  If there's an error, returns the undefined value.
	       This call is actually implemented in terms of recvfrom(2)
	       system call.  See "UDP: Message Passing" in perlipc for
	       examples.

	       Note the characters: depending on the status of the socket,
	       either (8-bit) bytes or characters are received.	 By default
	       all sockets operate on bytes, but for example if the socket has
	       been changed using binmode() to operate with the
	       ":encoding(utf8)" I/O layer (see the "open" pragma, open), the
	       I/O will operate on UTF-8 encoded Unicode characters, not
	       bytes.  Similarly for the ":encoding" pragma: in that case
	       pretty much any characters can be read.

       redo LABEL
       redo    The "redo" command restarts the loop block without evaluating
	       the conditional again.  The "continue" block, if any, is not
	       executed.  If the LABEL is omitted, the command refers to the
	       innermost enclosing loop.  Programs that want to lie to
	       themselves about what was just input normally use this command:

		   # a simpleminded Pascal comment stripper
		   # (warning: assumes no { or } in strings)
		   LINE: while (<STDIN>) {
		       while (s|({.*}.*){.*}|$1 |) {}
		       s|{.*}| |;
		       if (s|{.*| |) {
			   $front = $_;
			   while (<STDIN>) {
			       if (/}/) {      # end of comment?
				   s|^|$front\{|;
				   redo LINE;
			       }
			   }
		       }
		       print;
		   }

	       "redo" cannot be used to retry a block which returns a value
	       such as "eval {}", "sub {}" or "do {}", and should not be used
	       to exit a grep() or map() operation.

	       Note that a block by itself is semantically identical to a loop
	       that executes once.  Thus "redo" inside such a block will
	       effectively turn it into a looping construct.

	       See also "continue" for an illustration of how "last", "next",
	       and "redo" work.

       ref EXPR
       ref     Returns a non-empty string if EXPR is a reference, the empty
	       string otherwise. If EXPR is not specified, $_ will be used.
	       The value returned depends on the type of thing the reference
	       is a reference to.  Builtin types include:

		   SCALAR
		   ARRAY
		   HASH
		   CODE
		   REF
		   GLOB
		   LVALUE
		   FORMAT
		   IO
		   VSTRING
		   Regexp

	       If the referenced object has been blessed into a package, then
	       that package name is returned instead.  You can think of "ref"
	       as a "typeof" operator.

		   if (ref($r) eq "HASH") {
		       print "r is a reference to a hash.\n";
		   }
		   unless (ref($r)) {
		       print "r is not a reference at all.\n";
		   }

	       The return value "LVALUE" indicates a reference to an lvalue
	       that is not a variable. You get this from taking the reference
	       of function calls like "pos()" or "substr()". "VSTRING" is
	       returned if the reference points to a version string.

	       The result "Regexp" indicates that the argument is a regular
	       expression resulting from "qr//".

	       See also perlref.

       rename OLDNAME,NEWNAME
	       Changes the name of a file; an existing file NEWNAME will be
	       clobbered.  Returns true for success, false otherwise.

	       Behavior of this function varies wildly depending on your
	       system implementation.  For example, it will usually not work
	       across file system boundaries, even though the system mv
	       command sometimes compensates for this.	Other restrictions
	       include whether it works on directories, open files, or pre-
	       existing files.	Check perlport and either the rename(2)
	       manpage or equivalent system documentation for details.

	       For a platform independent "move" function look at the
	       File::Copy module.

       require VERSION
       require EXPR
       require Demands a version of Perl specified by VERSION, or demands some
	       semantics specified by EXPR or by $_ if EXPR is not supplied.

	       VERSION may be either a numeric argument such as 5.006, which
	       will be compared to $], or a literal of the form v5.6.1, which
	       will be compared to $^V (aka $PERL_VERSION).  A fatal error is
	       produced at run time if VERSION is greater than the version of
	       the current Perl interpreter.  Compare with "use", which can do
	       a similar check at compile time.

	       Specifying VERSION as a literal of the form v5.6.1 should
	       generally be avoided, because it leads to misleading error
	       messages under earlier versions of Perl that do not support
	       this syntax.  The equivalent numeric version should be used
	       instead.

		   require v5.6.1;     # run time version check
		   require 5.6.1;      # ditto
		   require 5.006_001;  # ditto; preferred for backwards compatibility

	       Otherwise, "require" demands that a library file be included if
	       it hasn't already been included.	 The file is included via the
	       do-FILE mechanism, which is essentially just a variety of
	       "eval" with the caveat that lexical variables in the invoking
	       script will be invisible to the included code.  Has semantics
	       similar to the following subroutine:

		   sub require {
		      my ($filename) = @_;
		      if (exists $INC{$filename}) {
			  return 1 if $INC{$filename};
			  die "Compilation failed in require";
		      }
		      my ($realfilename,$result);
		      ITER: {
			  foreach $prefix (@INC) {
			      $realfilename = "$prefix/$filename";
			      if (-f $realfilename) {
				  $INC{$filename} = $realfilename;
				  $result = do $realfilename;
				  last ITER;
			      }
			  }
			  die "Can't find $filename in \@INC";
		      }
		      if ($@) {
			  $INC{$filename} = undef;
			  die $@;
		      } elsif (!$result) {
			  delete $INC{$filename};
			  die "$filename did not return true value";
		      } else {
			  return $result;
		      }
		   }

	       Note that the file will not be included twice under the same
	       specified name.

	       The file must return true as the last statement to indicate
	       successful execution of any initialization code, so it's
	       customary to end such a file with "1;" unless you're sure it'll
	       return true otherwise.  But it's better just to put the "1;",
	       in case you add more statements.

	       If EXPR is a bareword, the require assumes a ".pm" extension
	       and replaces "::" with "/" in the filename for you, to make it
	       easy to load standard modules.  This form of loading of modules
	       does not risk altering your namespace.

	       In other words, if you try this:

		       require Foo::Bar;    # a splendid bareword

	       The require function will actually look for the "Foo/Bar.pm"
	       file in the directories specified in the @INC array.

	       But if you try this:

		       $class = 'Foo::Bar';
		       require $class;	    # $class is not a bareword
		   #or
		       require "Foo::Bar";  # not a bareword because of the ""

	       The require function will look for the "Foo::Bar" file in the
	       @INC array and will complain about not finding "Foo::Bar"
	       there.  In this case you can do:

		       eval "require $class";

	       Now that you understand how "require" looks for files in the
	       case of a bareword argument, there is a little extra
	       functionality going on behind the scenes.  Before "require"
	       looks for a ".pm" extension, it will first look for a similar
	       filename with a ".pmc" extension. If this file is found, it
	       will be loaded in place of any file ending in a ".pm"
	       extension.

	       You can also insert hooks into the import facility, by putting
	       directly Perl code into the @INC array.	There are three forms
	       of hooks: subroutine references, array references and blessed
	       objects.

	       Subroutine references are the simplest case.  When the
	       inclusion system walks through @INC and encounters a
	       subroutine, this subroutine gets called with two parameters,
	       the first being a reference to itself, and the second the name
	       of the file to be included (e.g. "Foo/Bar.pm").	The subroutine
	       should return nothing, or a list of up to three values in the
	       following order:

	       1.  A filehandle, from which the file will be read.

	       2.  A reference to a subroutine. If there is no filehandle
		   (previous item), then this subroutine is expected to
		   generate one line of source code per call, writing the line
		   into $_ and returning 1, then returning 0 at "end of file".
		   If there is a filehandle, then the subroutine will be
		   called to act as a simple source filter, with the line as
		   read in $_.	Again, return 1 for each valid line, and 0
		   after all lines have been returned.

	       3.  Optional state for the subroutine. The state is passed in
		   as $_[1]. A reference to the subroutine itself is passed in
		   as $_[0].

	       If an empty list, "undef", or nothing that matches the first 3
	       values above is returned then "require" will look at the
	       remaining elements of @INC.  Note that this file handle must be
	       a real file handle (strictly a typeglob, or reference to a
	       typeglob, blessed or unblessed) - tied file handles will be
	       ignored and return value processing will stop there.

	       If the hook is an array reference, its first element must be a
	       subroutine reference.  This subroutine is called as above, but
	       the first parameter is the array reference.  This enables to
	       pass indirectly some arguments to the subroutine.

	       In other words, you can write:

		   push @INC, \&my_sub;
		   sub my_sub {
		       my ($coderef, $filename) = @_;  # $coderef is \&my_sub
		       ...
		   }

	       or:

		   push @INC, [ \&my_sub, $x, $y, ... ];
		   sub my_sub {
		       my ($arrayref, $filename) = @_;
		       # Retrieve $x, $y, ...
		       my @parameters = @$arrayref[1..$#$arrayref];
		       ...
		   }

	       If the hook is an object, it must provide an INC method that
	       will be called as above, the first parameter being the object
	       itself.	(Note that you must fully qualify the sub's name, as
	       unqualified "INC" is always forced into package "main".)	 Here
	       is a typical code layout:

		   # In Foo.pm
		   package Foo;
		   sub new { ... }
		   sub Foo::INC {
		       my ($self, $filename) = @_;
		       ...
		   }

		   # In the main program
		   push @INC, Foo->new(...);

	       Note that these hooks are also permitted to set the %INC entry
	       corresponding to the files they have loaded. See "%INC" in
	       perlvar.

	       For a yet-more-powerful import facility, see "use" and perlmod.

       reset EXPR
       reset   Generally used in a "continue" block at the end of a loop to
	       clear variables and reset "??" searches so that they work
	       again.  The expression is interpreted as a list of single
	       characters (hyphens allowed for ranges).	 All variables and
	       arrays beginning with one of those letters are reset to their
	       pristine state.	If the expression is omitted, one-match
	       searches ("?pattern?") are reset to match again.	 Resets only
	       variables or searches in the current package.  Always returns
	       1.  Examples:

		   reset 'X';	       # reset all X variables
		   reset 'a-z';	       # reset lower case variables
		   reset;	       # just reset ?one-time? searches

	       Resetting "A-Z" is not recommended because you'll wipe out your
	       @ARGV and @INC arrays and your %ENV hash.  Resets only package
	       variables--lexical variables are unaffected, but they clean
	       themselves up on scope exit anyway, so you'll probably want to
	       use them instead.  See "my".

       return EXPR
       return  Returns from a subroutine, "eval", or "do FILE" with the value
	       given in EXPR.  Evaluation of EXPR may be in list, scalar, or
	       void context, depending on how the return value will be used,
	       and the context may vary from one execution to the next (see
	       "wantarray").  If no EXPR is given, returns an empty list in
	       list context, the undefined value in scalar context, and (of
	       course) nothing at all in a void context.

	       (Note that in the absence of an explicit "return", a
	       subroutine, eval, or do FILE will automatically return the
	       value of the last expression evaluated.)

       reverse LIST
	       In list context, returns a list value consisting of the
	       elements of LIST in the opposite order.	In scalar context,
	       concatenates the elements of LIST and returns a string value
	       with all characters in the opposite order.

		   print join(", ", reverse "world", "Hello"); # Hello, world

		   print scalar reverse "dlrow ,", "olleH";    # Hello, world

	       Used without arguments in scalar context, reverse() reverses
	       $_.

		   $_ = "dlrow ,olleH";
		   print reverse;			       # No output, list context
		   print scalar reverse;		       # Hello, world

	       This operator is also handy for inverting a hash, although
	       there are some caveats.	If a value is duplicated in the
	       original hash, only one of those can be represented as a key in
	       the inverted hash.  Also, this has to unwind one hash and build
	       a whole new one, which may take some time on a large hash, such
	       as from a DBM file.

		   %by_name = reverse %by_address;     # Invert the hash

       rewinddir DIRHANDLE
	       Sets the current position to the beginning of the directory for
	       the "readdir" routine on DIRHANDLE.

       rindex STR,SUBSTR,POSITION
       rindex STR,SUBSTR
	       Works just like index() except that it returns the position of
	       the last occurrence of SUBSTR in STR.  If POSITION is
	       specified, returns the last occurrence beginning at or before
	       that position.

       rmdir FILENAME
       rmdir   Deletes the directory specified by FILENAME if that directory
	       is empty.  If it succeeds it returns true, otherwise it returns
	       false and sets $! (errno).  If FILENAME is omitted, uses $_.

	       To remove a directory tree recursively ("rm -rf" on unix) look
	       at the "rmtree" function of the File::Path module.

       s///    The substitution operator.  See "Regexp Quote-Like Operators"
	       in perlop.

       say FILEHANDLE LIST
       say LIST
       say     Just like "print", but implicitly appends a newline.  "say
	       LIST" is simply an abbreviation for "{ local $\ = "\n"; print
	       LIST }".

	       This keyword is only available when the "say" feature is
	       enabled: see feature.

       scalar EXPR
	       Forces EXPR to be interpreted in scalar context and returns the
	       value of EXPR.

		   @counts = ( scalar @a, scalar @b, scalar @c );

	       There is no equivalent operator to force an expression to be
	       interpolated in list context because in practice, this is never
	       needed.	If you really wanted to do so, however, you could use
	       the construction "@{[ (some expression) ]}", but usually a
	       simple "(some expression)" suffices.

	       Because "scalar" is unary operator, if you accidentally use for
	       EXPR a parenthesized list, this behaves as a scalar comma
	       expression, evaluating all but the last element in void context
	       and returning the final element evaluated in scalar context.
	       This is seldom what you want.

	       The following single statement:

		       print uc(scalar(&foo,$bar)),$baz;

	       is the moral equivalent of these two:

		       &foo;
		       print(uc($bar),$baz);

	       See perlop for more details on unary operators and the comma
	       operator.

       seek FILEHANDLE,POSITION,WHENCE
	       Sets FILEHANDLE's position, just like the "fseek" call of
	       "stdio".	 FILEHANDLE may be an expression whose value gives the
	       name of the filehandle.	The values for WHENCE are 0 to set the
	       new position in bytes to POSITION, 1 to set it to the current
	       position plus POSITION, and 2 to set it to EOF plus POSITION
	       (typically negative).  For WHENCE you may use the constants
	       "SEEK_SET", "SEEK_CUR", and "SEEK_END" (start of the file,
	       current position, end of the file) from the Fcntl module.
	       Returns 1 upon success, 0 otherwise.

	       Note the in bytes: even if the filehandle has been set to
	       operate on characters (for example by using the
	       ":encoding(utf8)" open layer), tell() will return byte offsets,
	       not character offsets (because implementing that would render
	       seek() and tell() rather slow).

	       If you want to position file for "sysread" or "syswrite", don't
	       use "seek"--buffering makes its effect on the file's system
	       position unpredictable and non-portable.	 Use "sysseek"
	       instead.

	       Due to the rules and rigors of ANSI C, on some systems you have
	       to do a seek whenever you switch between reading and writing.
	       Amongst other things, this may have the effect of calling
	       stdio's clearerr(3).  A WHENCE of 1 ("SEEK_CUR") is useful for
	       not moving the file position:

		   seek(TEST,0,1);

	       This is also useful for applications emulating "tail -f".  Once
	       you hit EOF on your read, and then sleep for a while, you might
	       have to stick in a seek() to reset things.  The "seek" doesn't
	       change the current position, but it does clear the end-of-file
	       condition on the handle, so that the next "<FILE>" makes Perl
	       try again to read something.  We hope.

	       If that doesn't work (some IO implementations are particularly
	       cantankerous), then you may need something more like this:

		   for (;;) {
		       for ($curpos = tell(FILE); $_ = <FILE>;
			    $curpos = tell(FILE)) {
			   # search for some stuff and put it into files
		       }
		       sleep($for_a_while);
		       seek(FILE, $curpos, 0);
		   }

       seekdir DIRHANDLE,POS
	       Sets the current position for the "readdir" routine on
	       DIRHANDLE.  POS must be a value returned by "telldir".
	       "seekdir" also has the same caveats about possible directory
	       compaction as the corresponding system library routine.

       select FILEHANDLE
       select  Returns the currently selected filehandle.  If FILEHANDLE is
	       supplied, sets the new current default filehandle for output.
	       This has two effects: first, a "write" or a "print" without a
	       filehandle will default to this FILEHANDLE.  Second, references
	       to variables related to output will refer to this output
	       channel.	 For example, if you have to set the top of form
	       format for more than one output channel, you might do the
	       following:

		   select(REPORT1);
		   $^ = 'report1_top';
		   select(REPORT2);
		   $^ = 'report2_top';

	       FILEHANDLE may be an expression whose value gives the name of
	       the actual filehandle.  Thus:

		   $oldfh = select(STDERR); $| = 1; select($oldfh);

	       Some programmers may prefer to think of filehandles as objects
	       with methods, preferring to write the last example as:

		   use IO::Handle;
		   STDERR->autoflush(1);

       select RBITS,WBITS,EBITS,TIMEOUT
	       This calls the select(2) system call with the bit masks
	       specified, which can be constructed using "fileno" and "vec",
	       along these lines:

		   $rin = $win = $ein = '';
		   vec($rin,fileno(STDIN),1) = 1;
		   vec($win,fileno(STDOUT),1) = 1;
		   $ein = $rin | $win;

	       If you want to select on many filehandles you might wish to
	       write a subroutine:

		   sub fhbits {
		       my(@fhlist) = split(' ',$_[0]);
		       my($bits);
		       for (@fhlist) {
			   vec($bits,fileno($_),1) = 1;
		       }
		       $bits;
		   }
		   $rin = fhbits('STDIN TTY SOCK');

	       The usual idiom is:

		   ($nfound,$timeleft) =
		     select($rout=$rin, $wout=$win, $eout=$ein, $timeout);

	       or to block until something becomes ready just do this

		   $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);

	       Most systems do not bother to return anything useful in
	       $timeleft, so calling select() in scalar context just returns
	       $nfound.

	       Any of the bit masks can also be undef.	The timeout, if
	       specified, is in seconds, which may be fractional.  Note: not
	       all implementations are capable of returning the $timeleft.  If
	       not, they always return $timeleft equal to the supplied
	       $timeout.

	       You can effect a sleep of 250 milliseconds this way:

		   select(undef, undef, undef, 0.25);

	       Note that whether "select" gets restarted after signals (say,
	       SIGALRM) is implementation-dependent.  See also perlport for
	       notes on the portability of "select".

	       On error, "select" behaves like the select(2) system call : it
	       returns -1 and sets $!.

	       Note: on some Unixes, the select(2) system call may report a
	       socket file descriptor as "ready for reading", when actually no
	       data is available, thus a subsequent read blocks. It can be
	       avoided using always the O_NONBLOCK flag on the socket. See
	       select(2) and fcntl(2) for further details.

	       WARNING: One should not attempt to mix buffered I/O (like
	       "read" or <FH>) with "select", except as permitted by POSIX,
	       and even then only on POSIX systems.  You have to use "sysread"
	       instead.

       semctl ID,SEMNUM,CMD,ARG
	       Calls the System V IPC function "semctl".  You'll probably have
	       to say

		   use IPC::SysV;

	       first to get the correct constant definitions.  If CMD is
	       IPC_STAT or GETALL, then ARG must be a variable that will hold
	       the returned semid_ds structure or semaphore value array.
	       Returns like "ioctl": the undefined value for error, ""0 but
	       true"" for zero, or the actual return value otherwise.  The ARG
	       must consist of a vector of native short integers, which may be
	       created with "pack("s!",(0)x$nsem)".  See also "SysV IPC" in
	       perlipc, "IPC::SysV", "IPC::Semaphore" documentation.

       semget KEY,NSEMS,FLAGS
	       Calls the System V IPC function semget.	Returns the semaphore
	       id, or the undefined value if there is an error.	 See also
	       "SysV IPC" in perlipc, "IPC::SysV", "IPC::SysV::Semaphore"
	       documentation.

       semop KEY,OPSTRING
	       Calls the System V IPC function semop to perform semaphore
	       operations such as signalling and waiting.  OPSTRING must be a
	       packed array of semop structures.  Each semop structure can be
	       generated with "pack("s!3", $semnum, $semop, $semflag)".	 The
	       length of OPSTRING implies the number of semaphore operations.
	       Returns true if successful, or false if there is an error.  As
	       an example, the following code waits on semaphore $semnum of
	       semaphore id $semid:

		   $semop = pack("s!3", $semnum, -1, 0);
		   die "Semaphore trouble: $!\n" unless semop($semid, $semop);

	       To signal the semaphore, replace "-1" with 1.  See also "SysV
	       IPC" in perlipc, "IPC::SysV", and "IPC::SysV::Semaphore"
	       documentation.

       send SOCKET,MSG,FLAGS,TO
       send SOCKET,MSG,FLAGS
	       Sends a message on a socket.  Attempts to send the scalar MSG
	       to the SOCKET filehandle.  Takes the same flags as the system
	       call of the same name.  On unconnected sockets you must specify
	       a destination to send TO, in which case it does a C "sendto".
	       Returns the number of characters sent, or the undefined value
	       if there is an error.  The C system call sendmsg(2) is
	       currently unimplemented.	 See "UDP: Message Passing" in perlipc
	       for examples.

	       Note the characters: depending on the status of the socket,
	       either (8-bit) bytes or characters are sent.  By default all
	       sockets operate on bytes, but for example if the socket has
	       been changed using binmode() to operate with the
	       ":encoding(utf8)" I/O layer (see "open", or the "open" pragma,
	       open), the I/O will operate on UTF-8 encoded Unicode
	       characters, not bytes.  Similarly for the ":encoding" pragma:
	       in that case pretty much any characters can be sent.

       setpgrp PID,PGRP
	       Sets the current process group for the specified PID, 0 for the
	       current process.	 Will produce a fatal error if used on a
	       machine that doesn't implement POSIX setpgid(2) or BSD
	       setpgrp(2).  If the arguments are omitted, it defaults to
	       "0,0".  Note that the BSD 4.2 version of "setpgrp" does not
	       accept any arguments, so only "setpgrp(0,0)" is portable.  See
	       also "POSIX::setsid()".

       setpriority WHICH,WHO,PRIORITY
	       Sets the current priority for a process, a process group, or a
	       user.  (See setpriority(2).)  Will produce a fatal error if
	       used on a machine that doesn't implement setpriority(2).

       setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
	       Sets the socket option requested.  Returns undefined if there
	       is an error.  Use integer constants provided by the "Socket"
	       module for LEVEL and OPNAME.  Values for LEVEL can also be
	       obtained from getprotobyname.  OPTVAL might either be a packed
	       string or an integer.  An integer OPTVAL is shorthand for
	       pack("i", OPTVAL).

	       An example disabling the Nagle's algorithm for a socket:

		   use Socket qw(IPPROTO_TCP TCP_NODELAY);
		   setsockopt($socket, IPPROTO_TCP, TCP_NODELAY, 1);

       shift ARRAY
       shift   Shifts the first value of the array off and returns it,
	       shortening the array by 1 and moving everything down.  If there
	       are no elements in the array, returns the undefined value.  If
	       ARRAY is omitted, shifts the @_ array within the lexical scope
	       of subroutines and formats, and the @ARGV array outside of a
	       subroutine and also within the lexical scopes established by
	       the "eval STRING", "BEGIN {}", "INIT {}", "CHECK {}",
	       "UNITCHECK {}" and "END {}" constructs.

	       See also "unshift", "push", and "pop".  "shift" and "unshift"
	       do the same thing to the left end of an array that "pop" and
	       "push" do to the right end.

       shmctl ID,CMD,ARG
	       Calls the System V IPC function shmctl.	You'll probably have
	       to say

		   use IPC::SysV;

	       first to get the correct constant definitions.  If CMD is
	       "IPC_STAT", then ARG must be a variable that will hold the
	       returned "shmid_ds" structure.  Returns like ioctl: the
	       undefined value for error, "0 but true" for zero, or the actual
	       return value otherwise.	See also "SysV IPC" in perlipc and
	       "IPC::SysV" documentation.

       shmget KEY,SIZE,FLAGS
	       Calls the System V IPC function shmget.	Returns the shared
	       memory segment id, or the undefined value if there is an error.
	       See also "SysV IPC" in perlipc and "IPC::SysV" documentation.

       shmread ID,VAR,POS,SIZE
       shmwrite ID,STRING,POS,SIZE
	       Reads or writes the System V shared memory segment ID starting
	       at position POS for size SIZE by attaching to it, copying
	       in/out, and detaching from it.  When reading, VAR must be a
	       variable that will hold the data read.  When writing, if STRING
	       is too long, only SIZE bytes are used; if STRING is too short,
	       nulls are written to fill out SIZE bytes.  Return true if
	       successful, or false if there is an error.  shmread() taints
	       the variable. See also "SysV IPC" in perlipc, "IPC::SysV"
	       documentation, and the "IPC::Shareable" module from CPAN.

       shutdown SOCKET,HOW
	       Shuts down a socket connection in the manner indicated by HOW,
	       which has the same interpretation as in the system call of the
	       same name.

		   shutdown(SOCKET, 0);	   # I/we have stopped reading data
		   shutdown(SOCKET, 1);	   # I/we have stopped writing data
		   shutdown(SOCKET, 2);	   # I/we have stopped using this socket

	       This is useful with sockets when you want to tell the other
	       side you're done writing but not done reading, or vice versa.
	       It's also a more insistent form of close because it also
	       disables the file descriptor in any forked copies in other
	       processes.

	       Returns 1 for success. In the case of error, returns "undef" if
	       the first argument is not a valid filehandle, or returns 0 and
	       sets $! for any other failure.

       sin EXPR
       sin     Returns the sine of EXPR (expressed in radians).	 If EXPR is
	       omitted, returns sine of $_.

	       For the inverse sine operation, you may use the
	       "Math::Trig::asin" function, or use this relation:

		   sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) }

       sleep EXPR
       sleep   Causes the script to sleep for EXPR seconds, or forever if no
	       EXPR.  Returns the number of seconds actually slept.

	       May be interrupted if the process receives a signal such as
	       "SIGALRM".

		   eval {
		       local $SIG{ALARM} = sub { die "Alarm!\n" };
		       sleep;
		   };
		   die $@ unless $@ eq "Alarm!\n";

	       You probably cannot mix "alarm" and "sleep" calls, because
	       "sleep" is often implemented using "alarm".

	       On some older systems, it may sleep up to a full second less
	       than what you requested, depending on how it counts seconds.
	       Most modern systems always sleep the full amount.  They may
	       appear to sleep longer than that, however, because your process
	       might not be scheduled right away in a busy multitasking
	       system.

	       For delays of finer granularity than one second, the
	       Time::HiRes module (from CPAN, and starting from Perl 5.8 part
	       of the standard distribution) provides usleep().	 You may also
	       use Perl's four-argument version of select() leaving the first
	       three arguments undefined, or you might be able to use the
	       "syscall" interface to access setitimer(2) if your system
	       supports it. See perlfaq8 for details.

	       See also the POSIX module's "pause" function.

       socket SOCKET,DOMAIN,TYPE,PROTOCOL
	       Opens a socket of the specified kind and attaches it to
	       filehandle SOCKET.  DOMAIN, TYPE, and PROTOCOL are specified
	       the same as for the system call of the same name.  You should
	       "use Socket" first to get the proper definitions imported.  See
	       the examples in "Sockets: Client/Server Communication" in
	       perlipc.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened file descriptor, as determined
	       by the value of $^F.  See "$^F" in perlvar.

       socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
	       Creates an unnamed pair of sockets in the specified domain, of
	       the specified type.  DOMAIN, TYPE, and PROTOCOL are specified
	       the same as for the system call of the same name.  If
	       unimplemented, yields a fatal error.  Returns true if
	       successful.

	       On systems that support a close-on-exec flag on files, the flag
	       will be set for the newly opened file descriptors, as
	       determined by the value of $^F.	See "$^F" in perlvar.

	       Some systems defined "pipe" in terms of "socketpair", in which
	       a call to "pipe(Rdr, Wtr)" is essentially:

		   use Socket;
		   socketpair(Rdr, Wtr, AF_UNIX, SOCK_STREAM, PF_UNSPEC);
		   shutdown(Rdr, 1);	    # no more writing for reader
		   shutdown(Wtr, 0);	    # no more reading for writer

	       See perlipc for an example of socketpair use.  Perl 5.8 and
	       later will emulate socketpair using IP sockets to localhost if
	       your system implements sockets but not socketpair.

       sort SUBNAME LIST
       sort BLOCK LIST
       sort LIST
	       In list context, this sorts the LIST and returns the sorted
	       list value.  In scalar context, the behaviour of "sort()" is
	       undefined.

	       If SUBNAME or BLOCK is omitted, "sort"s in standard string
	       comparison order.  If SUBNAME is specified, it gives the name
	       of a subroutine that returns an integer less than, equal to, or
	       greater than 0, depending on how the elements of the list are
	       to be ordered.  (The "<=>" and "cmp" operators are extremely
	       useful in such routines.)  SUBNAME may be a scalar variable
	       name (unsubscripted), in which case the value provides the name
	       of (or a reference to) the actual subroutine to use.  In place
	       of a SUBNAME, you can provide a BLOCK as an anonymous, in-line
	       sort subroutine.

	       If the subroutine's prototype is "($$)", the elements to be
	       compared are passed by reference in @_, as for a normal
	       subroutine.  This is slower than unprototyped subroutines,
	       where the elements to be compared are passed into the
	       subroutine as the package global variables $a and $b (see
	       example below).	Note that in the latter case, it is usually
	       counter-productive to declare $a and $b as lexicals.

	       The values to be compared are always passed by reference and
	       should not be modified.

	       You also cannot exit out of the sort block or subroutine using
	       any of the loop control operators described in perlsyn or with
	       "goto".

	       When "use locale" is in effect, "sort LIST" sorts LIST
	       according to the current collation locale.  See perllocale.

	       sort() returns aliases into the original list, much as a for
	       loop's index variable aliases the list elements.	 That is,
	       modifying an element of a list returned by sort() (for example,
	       in a "foreach", "map" or "grep") actually modifies the element
	       in the original list.  This is usually something to be avoided
	       when writing clear code.

	       Perl 5.6 and earlier used a quicksort algorithm to implement
	       sort.  That algorithm was not stable, and could go quadratic.
	       (A stable sort preserves the input order of elements that
	       compare equal.  Although quicksort's run time is O(NlogN) when
	       averaged over all arrays of length N, the time can be O(N**2),
	       quadratic behavior, for some inputs.)  In 5.7, the quicksort
	       implementation was replaced with a stable mergesort algorithm
	       whose worst-case behavior is O(NlogN).  But benchmarks
	       indicated that for some inputs, on some platforms, the original
	       quicksort was faster.  5.8 has a sort pragma for limited
	       control of the sort.  Its rather blunt control of the
	       underlying algorithm may not persist into future Perls, but the
	       ability to characterize the input or output in implementation
	       independent ways quite probably will.  See the sort pragma.

	       Examples:

		   # sort lexically
		   @articles = sort @files;

		   # same thing, but with explicit sort routine
		   @articles = sort {$a cmp $b} @files;

		   # now case-insensitively
		   @articles = sort {uc($a) cmp uc($b)} @files;

		   # same thing in reversed order
		   @articles = sort {$b cmp $a} @files;

		   # sort numerically ascending
		   @articles = sort {$a <=> $b} @files;

		   # sort numerically descending
		   @articles = sort {$b <=> $a} @files;

		   # this sorts the %age hash by value instead of key
		   # using an in-line function
		   @eldest = sort { $age{$b} <=> $age{$a} } keys %age;

		   # sort using explicit subroutine name
		   sub byage {
		       $age{$a} <=> $age{$b};  # presuming numeric
		   }
		   @sortedclass = sort byage @class;

		   sub backwards { $b cmp $a }
		   @harry  = qw(dog cat x Cain Abel);
		   @george = qw(gone chased yz Punished Axed);
		   print sort @harry;
			   # prints AbelCaincatdogx
		   print sort backwards @harry;
			   # prints xdogcatCainAbel
		   print sort @george, 'to', @harry;
			   # prints AbelAxedCainPunishedcatchaseddoggonetoxyz

		   # inefficiently sort by descending numeric compare using
		   # the first integer after the first = sign, or the
		   # whole record case-insensitively otherwise

		   @new = sort {
		       ($b =~ /=(\d+)/)[0] <=> ($a =~ /=(\d+)/)[0]
					   ||
				   uc($a)  cmp	uc($b)
		   } @old;

		   # same thing, but much more efficiently;
		   # we'll build auxiliary indices instead
		   # for speed
		   @nums = @caps = ();
		   for (@old) {
		       push @nums, /=(\d+)/;
		       push @caps, uc($_);
		   }

		   @new = @old[ sort {
				       $nums[$b] <=> $nums[$a]
						||
				       $caps[$a] cmp $caps[$b]
				      } 0..$#old
			      ];

		   # same thing, but without any temps
		   @new = map { $_->[0] }
			  sort { $b->[1] <=> $a->[1]
					  ||
				 $a->[2] cmp $b->[2]
			  } map { [$_, /=(\d+)/, uc($_)] } @old;

		   # using a prototype allows you to use any comparison subroutine
		   # as a sort subroutine (including other package's subroutines)
		   package other;
		   sub backwards ($$) { $_[1] cmp $_[0]; }     # $a and $b are not set here

		   package main;
		   @new = sort other::backwards @old;

		   # guarantee stability, regardless of algorithm
		   use sort 'stable';
		   @new = sort { substr($a, 3, 5) cmp substr($b, 3, 5) } @old;

		   # force use of mergesort (not portable outside Perl 5.8)
		   use sort '_mergesort';  # note discouraging _
		   @new = sort { substr($a, 3, 5) cmp substr($b, 3, 5) } @old;

	       Warning: syntactical care is required when sorting the list
	       returned from a function. If you want to sort the list returned
	       by the function call "find_records(@key)", you can use:

		   @contact = sort { $a cmp $b } find_records @key;
		   @contact = sort +find_records(@key);
		   @contact = sort &find_records(@key);
		   @contact = sort(find_records(@key));

	       If instead you want to sort the array @key with the comparison
	       routine "find_records()" then you can use:

		   @contact = sort { find_records() } @key;
		   @contact = sort find_records(@key);
		   @contact = sort(find_records @key);
		   @contact = sort(find_records (@key));

	       If you're using strict, you must not declare $a and $b as
	       lexicals.  They are package globals.  That means that if you're
	       in the "main" package and type

		   @articles = sort {$b <=> $a} @files;

	       then $a and $b are $main::a and $main::b (or $::a and $::b),
	       but if you're in the "FooPack" package, it's the same as typing

		   @articles = sort {$FooPack::b <=> $FooPack::a} @files;

	       The comparison function is required to behave.  If it returns
	       inconsistent results (sometimes saying $x[1] is less than $x[2]
	       and sometimes saying the opposite, for example) the results are
	       not well-defined.

	       Because "<=>" returns "undef" when either operand is "NaN"
	       (not-a-number), and because "sort" will trigger a fatal error
	       unless the result of a comparison is defined, when sorting with
	       a comparison function like "$a <=> $b", be careful about lists
	       that might contain a "NaN".  The following example takes
	       advantage of the fact that "NaN != NaN" to eliminate any "NaN"s
	       from the input.

		   @result = sort { $a <=> $b } grep { $_ == $_ } @input;

       splice ARRAY,OFFSET,LENGTH,LIST
       splice ARRAY,OFFSET,LENGTH
       splice ARRAY,OFFSET
       splice ARRAY
	       Removes the elements designated by OFFSET and LENGTH from an
	       array, and replaces them with the elements of LIST, if any.  In
	       list context, returns the elements removed from the array.  In
	       scalar context, returns the last element removed, or "undef" if
	       no elements are removed.	 The array grows or shrinks as
	       necessary.  If OFFSET is negative then it starts that far from
	       the end of the array.  If LENGTH is omitted, removes everything
	       from OFFSET onward.  If LENGTH is negative, removes the
	       elements from OFFSET onward except for -LENGTH elements at the
	       end of the array.  If both OFFSET and LENGTH are omitted,
	       removes everything. If OFFSET is past the end of the array,
	       perl issues a warning, and splices at the end of the array.

	       The following equivalences hold (assuming "$[ == 0 and $#a >=
	       $i" )

		   push(@a,$x,$y)      splice(@a,@a,0,$x,$y)
		   pop(@a)	       splice(@a,-1)
		   shift(@a)	       splice(@a,0,1)
		   unshift(@a,$x,$y)   splice(@a,0,0,$x,$y)
		   $a[$i] = $y	       splice(@a,$i,1,$y)

	       Example, assuming array lengths are passed before arrays:

		   sub aeq {   # compare two list values
		       my(@a) = splice(@_,0,shift);
		       my(@b) = splice(@_,0,shift);
		       return 0 unless @a == @b;       # same len?
		       while (@a) {
			   return 0 if pop(@a) ne pop(@b);
		       }
		       return 1;
		   }
		   if (&aeq($len,@foo[1..$len],0+@bar,@bar)) { ... }

       split /PATTERN/,EXPR,LIMIT
       split /PATTERN/,EXPR
       split /PATTERN/
       split   Splits the string EXPR into a list of strings and returns that
	       list.  By default, empty leading fields are preserved, and
	       empty trailing ones are deleted.	 (If all fields are empty,
	       they are considered to be trailing.)

	       In scalar context, returns the number of fields found. In
	       scalar and void context it splits into the @_ array.  Use of
	       split in scalar and void context is deprecated, however,
	       because it clobbers your subroutine arguments.

	       If EXPR is omitted, splits the $_ string.  If PATTERN is also
	       omitted, splits on whitespace (after skipping any leading
	       whitespace).  Anything matching PATTERN is taken to be a
	       delimiter separating the fields.	 (Note that the delimiter may
	       be longer than one character.)

	       If LIMIT is specified and positive, it represents the maximum
	       number of fields the EXPR will be split into, though the actual
	       number of fields returned depends on the number of times
	       PATTERN matches within EXPR.  If LIMIT is unspecified or zero,
	       trailing null fields are stripped (which potential users of
	       "pop" would do well to remember).  If LIMIT is negative, it is
	       treated as if an arbitrarily large LIMIT had been specified.
	       Note that splitting an EXPR that evaluates to the empty string
	       always returns the empty list, regardless of the LIMIT
	       specified.

	       A pattern matching the null string (not to be confused with a
	       null pattern "//", which is just one member of the set of
	       patterns matching a null string) will split the value of EXPR
	       into separate characters at each point it matches that way.
	       For example:

		   print join(':', split(/ */, 'hi there')), "\n";

	       produces the output 'h:i:t:h:e:r:e'.

	       As a special case for "split", using the empty pattern "//"
	       specifically matches only the null string, and is not be
	       confused with the regular use of "//" to mean "the last
	       successful pattern match".  So, for "split", the following:

		   print join(':', split(//, 'hi there')), "\n";

	       produces the output 'h:i: :t:h:e:r:e'.

	       Empty leading fields are produced when there are positive-width
	       matches at the beginning of the string; a zero-width match at
	       the beginning of the string does not produce an empty field.
	       For example:

		  print join(':', split(/(?=\w)/, 'hi there!'));

	       produces the output 'h:i :t:h:e:r:e!'. Empty trailing fields,
	       on the other hand, are produced when there is a match at the
	       end of the string (and when LIMIT is given and is not 0),
	       regardless of the length of the match.  For example:

		  print join(':', split(//,   'hi there!', -1)), "\n";
		  print join(':', split(/\W/, 'hi there!', -1)), "\n";

	       produce the output 'h:i: :t:h:e:r:e:!:' and 'hi:there:',
	       respectively, both with an empty trailing field.

	       The LIMIT parameter can be used to split a line partially

		   ($login, $passwd, $remainder) = split(/:/, $_, 3);

	       When assigning to a list, if LIMIT is omitted, or zero, Perl
	       supplies a LIMIT one larger than the number of variables in the
	       list, to avoid unnecessary work.	 For the list above LIMIT
	       would have been 4 by default.  In time critical applications it
	       behooves you not to split into more fields than you really
	       need.

	       If the PATTERN contains parentheses, additional list elements
	       are created from each matching substring in the delimiter.

		   split(/([,-])/, "1-10,20", 3);

	       produces the list value

		   (1, '-', 10, ',', 20)

	       If you had the entire header of a normal Unix email message in
	       $header, you could split it up into fields and their values
	       this way:

		   $header =~ s/\n(?=\s)//g;  # fix continuation lines
		   %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);

	       The pattern "/PATTERN/" may be replaced with an expression to
	       specify patterns that vary at runtime.  (To do runtime
	       compilation only once, use "/$variable/o".)

	       As a special case, specifying a PATTERN of space (' ') will
	       split on white space just as "split" with no arguments does.
	       Thus, "split(' ')" can be used to emulate awk's default
	       behavior, whereas "split(/ /)" will give you as many null
	       initial fields as there are leading spaces.  A "split" on
	       "/\s+/" is like a "split(' ')" except that any leading
	       whitespace produces a null first field.	A "split" with no
	       arguments really does a "split(' ', $_)" internally.

	       A PATTERN of "/^/" is treated as if it were "/^/m", since it
	       isn't much use otherwise.

	       Example:

		   open(PASSWD, '/etc/passwd');
		   while (<PASSWD>) {
		       chomp;
		       ($login, $passwd, $uid, $gid,
			$gcos, $home, $shell) = split(/:/);
		       #...
		   }

	       As with regular pattern matching, any capturing parentheses
	       that are not matched in a "split()" will be set to "undef" when
	       returned:

		   @fields = split /(A)|B/, "1A2B3";
		   # @fields is (1, 'A', 2, undef, 3)

       sprintf FORMAT, LIST
	       Returns a string formatted by the usual "printf" conventions of
	       the C library function "sprintf".  See below for more details
	       and see sprintf(3) or printf(3) on your system for an
	       explanation of the general principles.

	       For example:

		       # Format number with up to 8 leading zeroes
		       $result = sprintf("%08d", $number);

		       # Round number to 3 digits after decimal point
		       $rounded = sprintf("%.3f", $number);

	       Perl does its own "sprintf" formatting--it emulates the C
	       function "sprintf", but it doesn't use it (except for floating-
	       point numbers, and even then only the standard modifiers are
	       allowed).  As a result, any non-standard extensions in your
	       local "sprintf" are not available from Perl.

	       Unlike "printf", "sprintf" does not do what you probably mean
	       when you pass it an array as your first argument. The array is
	       given scalar context, and instead of using the 0th element of
	       the array as the format, Perl will use the count of elements in
	       the array as the format, which is almost never useful.

	       Perl's "sprintf" permits the following universally-known
	       conversions:

		  %%   a percent sign
		  %c   a character with the given number
		  %s   a string
		  %d   a signed integer, in decimal
		  %u   an unsigned integer, in decimal
		  %o   an unsigned integer, in octal
		  %x   an unsigned integer, in hexadecimal
		  %e   a floating-point number, in scientific notation
		  %f   a floating-point number, in fixed decimal notation
		  %g   a floating-point number, in %e or %f notation

	       In addition, Perl permits the following widely-supported
	       conversions:

		  %X   like %x, but using upper-case letters
		  %E   like %e, but using an upper-case "E"
		  %G   like %g, but with an upper-case "E" (if applicable)
		  %b   an unsigned integer, in binary
		  %B   like %b, but using an upper-case "B" with the # flag
		  %p   a pointer (outputs the Perl value's address in hexadecimal)
		  %n   special: *stores* the number of characters output so far
		       into the next variable in the parameter list

	       Finally, for backward (and we do mean "backward")
	       compatibility, Perl permits these unnecessary but widely-
	       supported conversions:

		  %i   a synonym for %d
		  %D   a synonym for %ld
		  %U   a synonym for %lu
		  %O   a synonym for %lo
		  %F   a synonym for %f

	       Note that the number of exponent digits in the scientific
	       notation produced by %e, %E, %g and %G for numbers with the
	       modulus of the exponent less than 100 is system-dependent: it
	       may be three or less (zero-padded as necessary).	 In other
	       words, 1.23 times ten to the 99th may be either "1.23e99" or
	       "1.23e099".

	       Between the "%" and the format letter, you may specify a number
	       of additional attributes controlling the interpretation of the
	       format.	In order, these are:

	       format parameter index
		   An explicit format parameter index, such as "2$". By
		   default sprintf will format the next unused argument in the
		   list, but this allows you to take the arguments out of
		   order, e.g.:

		     printf '%2$d %1$d', 12, 34;      # prints "34 12"
		     printf '%3$d %d %1$d', 1, 2, 3;  # prints "3 1 1"

	       flags
		   one or more of:

		      space   prefix non-negative number with a space
		      +	      prefix non-negative number with a plus sign
		      -	      left-justify within the field
		      0	      use zeros, not spaces, to right-justify
		      #	      ensure the leading "0" for any octal,
			      prefix non-zero hexadecimal with "0x" or "0X",
			      prefix non-zero binary with "0b" or "0B"

		   For example:

		     printf '<% d>',  12;   # prints "< 12>"
		     printf '<%+d>',  12;   # prints "<+12>"
		     printf '<%6s>',  12;   # prints "<	   12>"
		     printf '<%-6s>', 12;   # prints "<12    >"
		     printf '<%06s>', 12;   # prints "<000012>"
		     printf '<%#o>',  12;   # prints "<014>"
		     printf '<%#x>',  12;   # prints "<0xc>"
		     printf '<%#X>',  12;   # prints "<0XC>"
		     printf '<%#b>',  12;   # prints "<0b1100>"
		     printf '<%#B>',  12;   # prints "<0B1100>"

		   When a space and a plus sign are given as the flags at
		   once, a plus sign is used to prefix a positive number.

		     printf '<%+ d>', 12;   # prints "<+12>"
		     printf '<% +d>', 12;   # prints "<+12>"

		   When the # flag and a precision are given in the %o
		   conversion, the precision is incremented if it's necessary
		   for the leading "0".

		     printf '<%#.5o>', 012;	 # prints "<00012>"
		     printf '<%#.5o>', 012345;	 # prints "<012345>"
		     printf '<%#.0o>', 0;	 # prints "<0>"

	       vector flag
		   This flag tells perl to interpret the supplied string as a
		   vector of integers, one for each character in the string.
		   Perl applies the format to each integer in turn, then joins
		   the resulting strings with a separator (a dot "." by
		   default). This can be useful for displaying ordinal values
		   of characters in arbitrary strings:

		     printf "%vd", "AB\x{100}";		  # prints "65.66.256"
		     printf "version is v%vd\n", $^V;	  # Perl's version

		   Put an asterisk "*" before the "v" to override the string
		   to use to separate the numbers:

		     printf "address is %*vX\n", ":", $addr;   # IPv6 address
		     printf "bits are %0*v8b\n", " ", $bits;   # random bitstring

		   You can also explicitly specify the argument number to use
		   for the join string using e.g. "*2$v":

		     printf '%*4$vX %*4$vX %*4$vX', @addr[1..3], ":";	# 3 IPv6 addresses

	       (minimum) width
		   Arguments are usually formatted to be only as wide as
		   required to display the given value. You can override the
		   width by putting a number here, or get the width from the
		   next argument (with "*") or from a specified argument (with
		   e.g. "*2$"):

		     printf '<%s>', "a";       # prints "<a>"
		     printf '<%6s>', "a";      # prints "<     a>"
		     printf '<%*s>', 6, "a";   # prints "<     a>"
		     printf '<%*2$s>', "a", 6; # prints "<     a>"
		     printf '<%2s>', "long";   # prints "<long>" (does not truncate)

		   If a field width obtained through "*" is negative, it has
		   the same effect as the "-" flag: left-justification.

	       precision, or maximum width
		   You can specify a precision (for numeric conversions) or a
		   maximum width (for string conversions) by specifying a "."
		   followed by a number.  For floating point formats, with the
		   exception of 'g' and 'G', this specifies the number of
		   decimal places to show (the default being 6), e.g.:

		     # these examples are subject to system-specific variation
		     printf '<%f>', 1;	  # prints "<1.000000>"
		     printf '<%.1f>', 1;  # prints "<1.0>"
		     printf '<%.0f>', 1;  # prints "<1>"
		     printf '<%e>', 10;	  # prints "<1.000000e+01>"
		     printf '<%.1e>', 10; # prints "<1.0e+01>"

		   For 'g' and 'G', this specifies the maximum number of
		   digits to show, including prior to the decimal point as
		   well as after it, e.g.:

		     # these examples are subject to system-specific variation
		     printf '<%g>', 1;	      # prints "<1>"
		     printf '<%.10g>', 1;     # prints "<1>"
		     printf '<%g>', 100;      # prints "<100>"
		     printf '<%.1g>', 100;    # prints "<1e+02>"
		     printf '<%.2g>', 100.01; # prints "<1e+02>"
		     printf '<%.5g>', 100.01; # prints "<100.01>"
		     printf '<%.4g>', 100.01; # prints "<100>"

		   For integer conversions, specifying a precision implies
		   that the output of the number itself should be zero-padded
		   to this width, where the 0 flag is ignored:

		     printf '<%.6d>', 1;      # prints "<000001>"
		     printf '<%+.6d>', 1;     # prints "<+000001>"
		     printf '<%-10.6d>', 1;   # prints "<000001	   >"
		     printf '<%10.6d>', 1;    # prints "<    000001>"
		     printf '<%010.6d>', 1;   # prints "<    000001>"
		     printf '<%+10.6d>', 1;   # prints "<   +000001>"

		     printf '<%.6x>', 1;      # prints "<000001>"
		     printf '<%#.6x>', 1;     # prints "<0x000001>"
		     printf '<%-10.6x>', 1;   # prints "<000001	   >"
		     printf '<%10.6x>', 1;    # prints "<    000001>"
		     printf '<%010.6x>', 1;   # prints "<    000001>"
		     printf '<%#10.6x>', 1;   # prints "<  0x000001>"

		   For string conversions, specifying a precision truncates
		   the string to fit in the specified width:

		     printf '<%.5s>', "truncated";   # prints "<trunc>"
		     printf '<%10.5s>', "truncated"; # prints "<     trunc>"

		   You can also get the precision from the next argument using
		   ".*":

		     printf '<%.6x>', 1;       # prints "<000001>"
		     printf '<%.*x>', 6, 1;    # prints "<000001>"

		   If a precision obtained through "*" is negative, it has the
		   same effect as no precision.

		     printf '<%.*s>',  7, "string";   # prints "<string>"
		     printf '<%.*s>',  3, "string";   # prints "<str>"
		     printf '<%.*s>',  0, "string";   # prints "<>"
		     printf '<%.*s>', -1, "string";   # prints "<string>"

		     printf '<%.*d>',  1, 0;   # prints "<0>"
		     printf '<%.*d>',  0, 0;   # prints "<>"
		     printf '<%.*d>', -1, 0;   # prints "<0>"

		   You cannot currently get the precision from a specified
		   number, but it is intended that this will be possible in
		   the future using e.g. ".*2$":

		     printf '<%.*2$x>', 1, 6;	# INVALID, but in future will print "<000001>"

	       size
		   For numeric conversions, you can specify the size to
		   interpret the number as using "l", "h", "V", "q", "L", or
		   "ll". For integer conversions ("d u o x X b i D U O"),
		   numbers are usually assumed to be whatever the default
		   integer size is on your platform (usually 32 or 64 bits),
		   but you can override this to use instead one of the
		   standard C types, as supported by the compiler used to
		   build Perl:

		      l		  interpret integer as C type "long" or "unsigned long"
		      h		  interpret integer as C type "short" or "unsigned short"
		      q, L or ll  interpret integer as C type "long long", "unsigned long long".
				  or "quads" (typically 64-bit integers)

		   The last will produce errors if Perl does not understand
		   "quads" in your installation. (This requires that either
		   the platform natively supports quads or Perl was
		   specifically compiled to support quads.) You can find out
		   whether your Perl supports quads via Config:

			   use Config;
			   ($Config{use64bitint} eq 'define' || $Config{longsize} >= 8) &&
				   print "quads\n";

		   For floating point conversions ("e f g E F G"), numbers are
		   usually assumed to be the default floating point size on
		   your platform (double or long double), but you can force
		   'long double' with "q", "L", or "ll" if your platform
		   supports them. You can find out whether your Perl supports
		   long doubles via Config:

			   use Config;
			   $Config{d_longdbl} eq 'define' && print "long doubles\n";

		   You can find out whether Perl considers 'long double' to be
		   the default floating point size to use on your platform via
		   Config:

			   use Config;
			   ($Config{uselongdouble} eq 'define') &&
				   print "long doubles by default\n";

		   It can also be the case that long doubles and doubles are
		   the same thing:

			   use Config;
			   ($Config{doublesize} == $Config{longdblsize}) &&
				   print "doubles are long doubles\n";

		   The size specifier "V" has no effect for Perl code, but it
		   is supported for compatibility with XS code; it means 'use
		   the standard size for a Perl integer (or floating-point
		   number)', which is already the default for Perl code.

	       order of arguments
		   Normally, sprintf takes the next unused argument as the
		   value to format for each format specification. If the
		   format specification uses "*" to require additional
		   arguments, these are consumed from the argument list in the
		   order in which they appear in the format specification
		   before the value to format. Where an argument is specified
		   using an explicit index, this does not affect the normal
		   order for the arguments (even when the explicitly specified
		   index would have been the next argument in any case).

		   So:

		     printf '<%*.*s>', $a, $b, $c;

		   would use $a for the width, $b for the precision and $c as
		   the value to format, while:

		     printf '<%*1$.*s>', $a, $b;

		   would use $a for the width and the precision, and $b as the
		   value to format.

		   Here are some more examples - beware that when using an
		   explicit index, the "$" may need to be escaped:

		     printf "%2\$d %d\n",    12, 34;		   # will print "34 12\n"
		     printf "%2\$d %d %d\n", 12, 34;		   # will print "34 12 34\n"
		     printf "%3\$d %d %d\n", 12, 34, 56;	   # will print "56 12 34\n"
		     printf "%2\$*3\$d %d\n", 12, 34, 3;	   # will print " 34 12\n"

	       If "use locale" is in effect, and POSIX::setlocale() has been
	       called, the character used for the decimal separator in
	       formatted floating point numbers is affected by the LC_NUMERIC
	       locale.	See perllocale and POSIX.

       sqrt EXPR
       sqrt    Return the square root of EXPR.	If EXPR is omitted, returns
	       square root of $_.  Only works on non-negative operands, unless
	       you've loaded the standard Math::Complex module.

		   use Math::Complex;
		   print sqrt(-2);    # prints 1.4142135623731i

       srand EXPR
       srand   Sets the random number seed for the "rand" operator.

	       The point of the function is to "seed" the "rand" function so
	       that "rand" can produce a different sequence each time you run
	       your program.

	       If srand() is not called explicitly, it is called implicitly at
	       the first use of the "rand" operator.  However, this was not
	       the case in versions of Perl before 5.004, so if your script
	       will run under older Perl versions, it should call "srand".

	       Most programs won't even call srand() at all, except those that
	       need a cryptographically-strong starting point rather than the
	       generally acceptable default, which is based on time of day,
	       process ID, and memory allocation, or the /dev/urandom device,
	       if available.

	       You can call srand($seed) with the same $seed to reproduce the
	       same sequence from rand(), but this is usually reserved for
	       generating predictable results for testing or debugging.
	       Otherwise, don't call srand() more than once in your program.

	       Do not call srand() (i.e. without an argument) more than once
	       in a script.  The internal state of the random number generator
	       should contain more entropy than can be provided by any seed,
	       so calling srand() again actually loses randomness.

	       Most implementations of "srand" take an integer and will
	       silently truncate decimal numbers.  This means "srand(42)" will
	       usually produce the same results as "srand(42.1)".  To be safe,
	       always pass "srand" an integer.

	       In versions of Perl prior to 5.004 the default seed was just
	       the current "time".  This isn't a particularly good seed, so
	       many old programs supply their own seed value (often "time ^
	       $$" or "time ^ ($$ + ($$ << 15))"), but that isn't necessary
	       any more.

	       For cryptographic purposes, however, you need something much
	       more random than the default seed.  Checksumming the compressed
	       output of one or more rapidly changing operating system status
	       programs is the usual method.  For example:

		   srand (time ^ $$ ^ unpack "%L*", `ps axww | gzip -f`);

	       If you're particularly concerned with this, see the
	       "Math::TrulyRandom" module in CPAN.

	       Frequently called programs (like CGI scripts) that simply use

		   time ^ $$

	       for a seed can fall prey to the mathematical property that

		   a^b == (a+1)^(b+1)

	       one-third of the time.  So don't do that.

       stat FILEHANDLE
       stat EXPR
       stat DIRHANDLE
       stat    Returns a 13-element list giving the status info for a file,
	       either the file opened via FILEHANDLE or DIRHANDLE, or named by
	       EXPR.  If EXPR is omitted, it stats $_.	Returns a null list if
	       the stat fails.	Typically used as follows:

		   ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
		      $atime,$mtime,$ctime,$blksize,$blocks)
			  = stat($filename);

	       Not all fields are supported on all filesystem types.  Here are
	       the meanings of the fields:

		 0 dev	    device number of filesystem
		 1 ino	    inode number
		 2 mode	    file mode  (type and permissions)
		 3 nlink    number of (hard) links to the file
		 4 uid	    numeric user ID of file's owner
		 5 gid	    numeric group ID of file's owner
		 6 rdev	    the device identifier (special files only)
		 7 size	    total size of file, in bytes
		 8 atime    last access time in seconds since the epoch
		 9 mtime    last modify time in seconds since the epoch
		10 ctime    inode change time in seconds since the epoch (*)
		11 blksize  preferred block size for file system I/O
		12 blocks   actual number of blocks allocated

	       (The epoch was at 00:00 January 1, 1970 GMT.)

	       (*) Not all fields are supported on all filesystem types.
	       Notably, the ctime field is non-portable.  In particular, you
	       cannot expect it to be a "creation time", see "Files and
	       Filesystems" in perlport for details.

	       If "stat" is passed the special filehandle consisting of an
	       underline, no stat is done, but the current contents of the
	       stat structure from the last "stat", "lstat", or filetest are
	       returned.  Example:

		   if (-x $file && (($d) = stat(_)) && $d < 0) {
		       print "$file is executable NFS file\n";
		   }

	       (This works on machines only for which the device number is
	       negative under NFS.)

	       Because the mode contains both the file type and its
	       permissions, you should mask off the file type portion and
	       (s)printf using a "%o" if you want to see the real permissions.

		   $mode = (stat($filename))[2];
		   printf "Permissions are %04o\n", $mode & 07777;

	       In scalar context, "stat" returns a boolean value indicating
	       success or failure, and, if successful, sets the information
	       associated with the special filehandle "_".

	       The File::stat module provides a convenient, by-name access
	       mechanism:

		   use File::stat;
		   $sb = stat($filename);
		   printf "File is %s, size is %s, perm %04o, mtime %s\n",
		       $filename, $sb->size, $sb->mode & 07777,
		       scalar localtime $sb->mtime;

	       You can import symbolic mode constants ("S_IF*") and functions
	       ("S_IS*") from the Fcntl module:

		   use Fcntl ':mode';

		   $mode = (stat($filename))[2];

		   $user_rwx	  = ($mode & S_IRWXU) >> 6;
		   $group_read	  = ($mode & S_IRGRP) >> 3;
		   $other_execute =  $mode & S_IXOTH;

		   printf "Permissions are %04o\n", S_IMODE($mode), "\n";

		   $is_setuid	  =  $mode & S_ISUID;
		   $is_directory  =  S_ISDIR($mode);

	       You could write the last two using the "-u" and "-d" operators.
	       The commonly available "S_IF*" constants are

		   # Permissions: read, write, execute, for user, group, others.

		   S_IRWXU S_IRUSR S_IWUSR S_IXUSR
		   S_IRWXG S_IRGRP S_IWGRP S_IXGRP
		   S_IRWXO S_IROTH S_IWOTH S_IXOTH

		   # Setuid/Setgid/Stickiness/SaveText.
		   # Note that the exact meaning of these is system dependent.

		   S_ISUID S_ISGID S_ISVTX S_ISTXT

		   # File types.  Not necessarily all are available on your system.

		   S_IFREG S_IFDIR S_IFLNK S_IFBLK S_IFCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT

		   # The following are compatibility aliases for S_IRUSR, S_IWUSR, S_IXUSR.

		   S_IREAD S_IWRITE S_IEXEC

	       and the "S_IF*" functions are

		   S_IMODE($mode)      the part of $mode containing the permission bits
				       and the setuid/setgid/sticky bits

		   S_IFMT($mode)       the part of $mode containing the file type
				       which can be bit-anded with e.g. S_IFREG
				       or with the following functions

		   # The operators -f, -d, -l, -b, -c, -p, and -S.

		   S_ISREG($mode) S_ISDIR($mode) S_ISLNK($mode)
		   S_ISBLK($mode) S_ISCHR($mode) S_ISFIFO($mode) S_ISSOCK($mode)

		   # No direct -X operator counterpart, but for the first one
		   # the -g operator is often equivalent.  The ENFMT stands for
		   # record flocking enforcement, a platform-dependent feature.

		   S_ISENFMT($mode) S_ISWHT($mode)

	       See your native chmod(2) and stat(2) documentation for more
	       details about the "S_*" constants.  To get status info for a
	       symbolic link instead of the target file behind the link, use
	       the "lstat" function.

       state EXPR
       state TYPE EXPR
       state EXPR : ATTRS
       state TYPE EXPR : ATTRS
	       "state" declares a lexically scoped variable, just like "my"
	       does.  However, those variables will never be reinitialized,
	       contrary to lexical variables that are reinitialized each time
	       their enclosing block is entered.

	       "state" variables are only enabled when the "feature 'state'"
	       pragma is in effect.  See feature.

       study SCALAR
       study   Takes extra time to study SCALAR ($_ if unspecified) in
	       anticipation of doing many pattern matches on the string before
	       it is next modified.  This may or may not save time, depending
	       on the nature and number of patterns you are searching on, and
	       on the distribution of character frequencies in the string to
	       be searched--you probably want to compare run times with and
	       without it to see which runs faster.  Those loops that scan for
	       many short constant strings (including the constant parts of
	       more complex patterns) will benefit most.  You may have only
	       one "study" active at a time--if you study a different scalar
	       the first is "unstudied".  (The way "study" works is this: a
	       linked list of every character in the string to be searched is
	       made, so we know, for example, where all the 'k' characters
	       are.  From each search string, the rarest character is
	       selected, based on some static frequency tables constructed
	       from some C programs and English text.  Only those places that
	       contain this "rarest" character are examined.)

	       For example, here is a loop that inserts index producing
	       entries before any line containing a certain pattern:

		   while (<>) {
		       study;
		       print ".IX foo\n"       if /\bfoo\b/;
		       print ".IX bar\n"       if /\bbar\b/;
		       print ".IX blurfl\n"    if /\bblurfl\b/;
		       # ...
		       print;
		   }

	       In searching for "/\bfoo\b/", only those locations in $_ that
	       contain "f" will be looked at, because "f" is rarer than "o".
	       In general, this is a big win except in pathological cases.
	       The only question is whether it saves you more time than it
	       took to build the linked list in the first place.

	       Note that if you have to look for strings that you don't know
	       till runtime, you can build an entire loop as a string and
	       "eval" that to avoid recompiling all your patterns all the
	       time.  Together with undefining $/ to input entire files as one
	       record, this can be very fast, often faster than specialized
	       programs like fgrep(1).	The following scans a list of files
	       (@files) for a list of words (@words), and prints out the names
	       of those files that contain a match:

		   $search = 'while (<>) { study;';
		   foreach $word (@words) {
		       $search .= "++\$seen{\$ARGV} if /\\b$word\\b/;\n";
		   }
		   $search .= "}";
		   @ARGV = @files;
		   undef $/;
		   eval $search;	       # this screams
		   $/ = "\n";	       # put back to normal input delimiter
		   foreach $file (sort keys(%seen)) {
		       print $file, "\n";
		   }

       sub NAME BLOCK
       sub NAME (PROTO) BLOCK
       sub NAME : ATTRS BLOCK
       sub NAME (PROTO) : ATTRS BLOCK
	       This is subroutine definition, not a real function per se.
	       Without a BLOCK it's just a forward declaration.	 Without a
	       NAME, it's an anonymous function declaration, and does actually
	       return a value: the CODE ref of the closure you just created.

	       See perlsub and perlref for details about subroutines and
	       references, and attributes and Attribute::Handlers for more
	       information about attributes.

       substr EXPR,OFFSET,LENGTH,REPLACEMENT
       substr EXPR,OFFSET,LENGTH
       substr EXPR,OFFSET
	       Extracts a substring out of EXPR and returns it.	 First
	       character is at offset 0, or whatever you've set $[ to (but
	       don't do that).	If OFFSET is negative (or more precisely, less
	       than $[), starts that far from the end of the string.  If
	       LENGTH is omitted, returns everything to the end of the string.
	       If LENGTH is negative, leaves that many characters off the end
	       of the string.

		   my $s = "The black cat climbed the green tree";
		   my $color  = substr $s, 4, 5;       # black
		   my $middle = substr $s, 4, -11;     # black cat climbed the
		   my $end    = substr $s, 14;	       # climbed the green tree
		   my $tail   = substr $s, -4;	       # tree
		   my $z      = substr $s, -4, 2;      # tr

	       You can use the substr() function as an lvalue, in which case
	       EXPR must itself be an lvalue.  If you assign something shorter
	       than LENGTH, the string will shrink, and if you assign
	       something longer than LENGTH, the string will grow to
	       accommodate it.	To keep the string the same length you may
	       need to pad or chop your value using "sprintf".

	       If OFFSET and LENGTH specify a substring that is partly outside
	       the string, only the part within the string is returned.	 If
	       the substring is beyond either end of the string, substr()
	       returns the undefined value and produces a warning.  When used
	       as an lvalue, specifying a substring that is entirely outside
	       the string is a fatal error.  Here's an example showing the
	       behavior for boundary cases:

		   my $name = 'fred';
		   substr($name, 4) = 'dy';	       # $name is now 'freddy'
		   my $null = substr $name, 6, 2;      # returns '' (no warning)
		   my $oops = substr $name, 7;	       # returns undef, with warning
		   substr($name, 7) = 'gap';	       # fatal error

	       An alternative to using substr() as an lvalue is to specify the
	       replacement string as the 4th argument.	This allows you to
	       replace parts of the EXPR and return what was there before in
	       one operation, just as you can with splice().

		   my $s = "The black cat climbed the green tree";
		   my $z = substr $s, 14, 7, "jumped from";    # climbed
		   # $s is now "The black cat jumped from the green tree"

	       Note that the lvalue returned by the 3-arg version of substr()
	       acts as a 'magic bullet'; each time it is assigned to, it
	       remembers which part of the original string is being modified;
	       for example:

		   $x = '1234';
		   for (substr($x,1,2)) {
		       $_ = 'a';   print $x,"\n";      # prints 1a4
		       $_ = 'xyz'; print $x,"\n";      # prints 1xyz4
		       $x = '56789';
		       $_ = 'pq';  print $x,"\n";      # prints 5pq9
		   }

	       Prior to Perl version 5.9.1, the result of using an lvalue
	       multiple times was unspecified.

       symlink OLDFILE,NEWFILE
	       Creates a new filename symbolically linked to the old filename.
	       Returns 1 for success, 0 otherwise.  On systems that don't
	       support symbolic links, produces a fatal error at run time.  To
	       check for that, use eval:

		   $symlink_exists = eval { symlink("",""); 1 };

       syscall NUMBER, LIST
	       Calls the system call specified as the first element of the
	       list, passing the remaining elements as arguments to the system
	       call.  If unimplemented, produces a fatal error.	 The arguments
	       are interpreted as follows: if a given argument is numeric, the
	       argument is passed as an int.  If not, the pointer to the
	       string value is passed.	You are responsible to make sure a
	       string is pre-extended long enough to receive any result that
	       might be written into a string.	You can't use a string literal
	       (or other read-only string) as an argument to "syscall" because
	       Perl has to assume that any string pointer might be written
	       through.	 If your integer arguments are not literals and have
	       never been interpreted in a numeric context, you may need to
	       add 0 to them to force them to look like numbers.  This
	       emulates the "syswrite" function (or vice versa):

		   require 'syscall.ph';	       # may need to run h2ph
		   $s = "hi there\n";
		   syscall(&SYS_write, fileno(STDOUT), $s, length $s);

	       Note that Perl supports passing of up to only 14 arguments to
	       your system call, which in practice should usually suffice.

	       Syscall returns whatever value returned by the system call it
	       calls.  If the system call fails, "syscall" returns "-1" and
	       sets $! (errno).	 Note that some system calls can legitimately
	       return "-1".  The proper way to handle such calls is to assign
	       "$!=0;" before the call and check the value of $! if syscall
	       returns "-1".

	       There's a problem with "syscall(&SYS_pipe)": it returns the
	       file number of the read end of the pipe it creates.  There is
	       no way to retrieve the file number of the other end.  You can
	       avoid this problem by using "pipe" instead.

       sysopen FILEHANDLE,FILENAME,MODE
       sysopen FILEHANDLE,FILENAME,MODE,PERMS
	       Opens the file whose filename is given by FILENAME, and
	       associates it with FILEHANDLE.  If FILEHANDLE is an expression,
	       its value is used as the name of the real filehandle wanted.
	       This function calls the underlying operating system's "open"
	       function with the parameters FILENAME, MODE, PERMS.

	       The possible values and flag bits of the MODE parameter are
	       system-dependent; they are available via the standard module
	       "Fcntl".	 See the documentation of your operating system's
	       "open" to see which values and flag bits are available.	You
	       may combine several flags using the "|"-operator.

	       Some of the most common values are "O_RDONLY" for opening the
	       file in read-only mode, "O_WRONLY" for opening the file in
	       write-only mode, and "O_RDWR" for opening the file in read-
	       write mode.

	       For historical reasons, some values work on almost every system
	       supported by perl: zero means read-only, one means write-only,
	       and two means read/write.  We know that these values do not
	       work under OS/390 & VM/ESA Unix and on the Macintosh; you
	       probably don't want to use them in new code.

	       If the file named by FILENAME does not exist and the "open"
	       call creates it (typically because MODE includes the "O_CREAT"
	       flag), then the value of PERMS specifies the permissions of the
	       newly created file.  If you omit the PERMS argument to
	       "sysopen", Perl uses the octal value 0666.  These permission
	       values need to be in octal, and are modified by your process's
	       current "umask".

	       In many systems the "O_EXCL" flag is available for opening
	       files in exclusive mode.	 This is not locking: exclusiveness
	       means here that if the file already exists, sysopen() fails.
	       "O_EXCL" may not work on network filesystems, and has no effect
	       unless the "O_CREAT" flag is set as well.  Setting
	       "O_CREAT|O_EXCL" prevents the file from being opened if it is a
	       symbolic link.  It does not protect against symbolic links in
	       the file's path.

	       Sometimes you may want to truncate an already-existing file.
	       This can be done using the "O_TRUNC" flag.  The behavior of
	       "O_TRUNC" with "O_RDONLY" is undefined.

	       You should seldom if ever use 0644 as argument to "sysopen",
	       because that takes away the user's option to have a more
	       permissive umask.  Better to omit it.  See the perlfunc(1)
	       entry on "umask" for more on this.

	       Note that "sysopen" depends on the fdopen() C library function.
	       On many UNIX systems, fdopen() is known to fail when file
	       descriptors exceed a certain value, typically 255. If you need
	       more file descriptors than that, consider rebuilding Perl to
	       use the "sfio" library, or perhaps using the POSIX::open()
	       function.

	       See perlopentut for a kinder, gentler explanation of opening
	       files.

       sysread FILEHANDLE,SCALAR,LENGTH,OFFSET
       sysread FILEHANDLE,SCALAR,LENGTH
	       Attempts to read LENGTH bytes of data into variable SCALAR from
	       the specified FILEHANDLE, using the system call read(2).	 It
	       bypasses buffered IO, so mixing this with other kinds of reads,
	       "print", "write", "seek", "tell", or "eof" can cause confusion
	       because the perlio or stdio layers usually buffers data.
	       Returns the number of bytes actually read, 0 at end of file, or
	       undef if there was an error (in the latter case $! is also
	       set).  SCALAR will be grown or shrunk so that the last byte
	       actually read is the last byte of the scalar after the read.

	       An OFFSET may be specified to place the read data at some place
	       in the string other than the beginning.	A negative OFFSET
	       specifies placement at that many characters counting backwards
	       from the end of the string.  A positive OFFSET greater than the
	       length of SCALAR results in the string being padded to the
	       required size with "\0" bytes before the result of the read is
	       appended.

	       There is no syseof() function, which is ok, since eof() doesn't
	       work very well on device files (like ttys) anyway.  Use
	       sysread() and check for a return value for 0 to decide whether
	       you're done.

	       Note that if the filehandle has been marked as ":utf8" Unicode
	       characters are read instead of bytes (the LENGTH, OFFSET, and
	       the return value of sysread() are in Unicode characters).  The
	       ":encoding(...)" layer implicitly introduces the ":utf8" layer.
	       See "binmode", "open", and the "open" pragma, open.

       sysseek FILEHANDLE,POSITION,WHENCE
	       Sets FILEHANDLE's system position in bytes using the system
	       call lseek(2).  FILEHANDLE may be an expression whose value
	       gives the name of the filehandle.  The values for WHENCE are 0
	       to set the new position to POSITION, 1 to set the it to the
	       current position plus POSITION, and 2 to set it to EOF plus
	       POSITION (typically negative).

	       Note the in bytes: even if the filehandle has been set to
	       operate on characters (for example by using the
	       ":encoding(utf8)" I/O layer), tell() will return byte offsets,
	       not character offsets (because implementing that would render
	       sysseek() very slow).

	       sysseek() bypasses normal buffered IO, so mixing this with
	       reads (other than "sysread", for example "<>" or read())
	       "print", "write", "seek", "tell", or "eof" may cause confusion.

	       For WHENCE, you may also use the constants "SEEK_SET",
	       "SEEK_CUR", and "SEEK_END" (start of the file, current
	       position, end of the file) from the Fcntl module.  Use of the
	       constants is also more portable than relying on 0, 1, and 2.
	       For example to define a "systell" function:

		       use Fcntl 'SEEK_CUR';
		       sub systell { sysseek($_[0], 0, SEEK_CUR) }

	       Returns the new position, or the undefined value on failure.  A
	       position of zero is returned as the string "0 but true"; thus
	       "sysseek" returns true on success and false on failure, yet you
	       can still easily determine the new position.

       system LIST
       system PROGRAM LIST
	       Does exactly the same thing as "exec LIST", except that a fork
	       is done first, and the parent process waits for the child
	       process to complete.  Note that argument processing varies
	       depending on the number of arguments.  If there is more than
	       one argument in LIST, or if LIST is an array with more than one
	       value, starts the program given by the first element of the
	       list with arguments given by the rest of the list.  If there is
	       only one scalar argument, the argument is checked for shell
	       metacharacters, and if there are any, the entire argument is
	       passed to the system's command shell for parsing (this is
	       "/bin/sh -c" on Unix platforms, but varies on other platforms).
	       If there are no shell metacharacters in the argument, it is
	       split into words and passed directly to "execvp", which is more
	       efficient.

	       Beginning with v5.6.0, Perl will attempt to flush all files
	       opened for output before any operation that may do a fork, but
	       this may not be supported on some platforms (see perlport).  To
	       be safe, you may need to set $| ($AUTOFLUSH in English) or call
	       the "autoflush()" method of "IO::Handle" on any open handles.

	       The return value is the exit status of the program as returned
	       by the "wait" call.  To get the actual exit value, shift right
	       by eight (see below). See also "exec".  This is not what you
	       want to use to capture the output from a command, for that you
	       should use merely backticks or "qx//", as described in
	       "`STRING`" in perlop.  Return value of -1 indicates a failure
	       to start the program or an error of the wait(2) system call
	       (inspect $! for the reason).

	       If you'd like to make "system" (and many other bits of Perl)
	       die on error, have a look at the autodie pragma.

	       Like "exec", "system" allows you to lie to a program about its
	       name if you use the "system PROGRAM LIST" syntax.  Again, see
	       "exec".

	       Since "SIGINT" and "SIGQUIT" are ignored during the execution
	       of "system", if you expect your program to terminate on receipt
	       of these signals you will need to arrange to do so yourself
	       based on the return value.

		   @args = ("command", "arg1", "arg2");
		   system(@args) == 0
			or die "system @args failed: $?"

	       If you'd like to manually inspect "system"'s failure, you can
	       check all possible failure modes by inspecting $? like this:

		   if ($? == -1) {
		       print "failed to execute: $!\n";
		   }
		   elsif ($? & 127) {
		       printf "child died with signal %d, %s coredump\n",
			   ($? & 127),	($? & 128) ? 'with' : 'without';
		   }
		   else {
		       printf "child exited with value %d\n", $? >> 8;
		   }

	       Alternatively you might inspect the value of
	       "${^CHILD_ERROR_NATIVE}" with the W*() calls of the POSIX
	       extension.

	       When the arguments get executed via the system shell, results
	       and return codes will be subject to its quirks and
	       capabilities.  See "`STRING`" in perlop and "exec" for details.

       syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET
       syswrite FILEHANDLE,SCALAR,LENGTH
       syswrite FILEHANDLE,SCALAR
	       Attempts to write LENGTH bytes of data from variable SCALAR to
	       the specified FILEHANDLE, using the system call write(2).  If
	       LENGTH is not specified, writes whole SCALAR.  It bypasses
	       buffered IO, so mixing this with reads (other than sysread()),
	       "print", "write", "seek", "tell", or "eof" may cause confusion
	       because the perlio and stdio layers usually buffers data.
	       Returns the number of bytes actually written, or "undef" if
	       there was an error (in this case the errno variable $! is also
	       set).  If the LENGTH is greater than the available data in the
	       SCALAR after the OFFSET, only as much data as is available will
	       be written.

	       An OFFSET may be specified to write the data from some part of
	       the string other than the beginning.  A negative OFFSET
	       specifies writing that many characters counting backwards from
	       the end of the string.  In the case the SCALAR is empty you can
	       use OFFSET but only zero offset.

	       Note that if the filehandle has been marked as ":utf8", Unicode
	       characters are written instead of bytes (the LENGTH, OFFSET,
	       and the return value of syswrite() are in UTF-8 encoded Unicode
	       characters).  The ":encoding(...)" layer implicitly introduces
	       the ":utf8" layer.  See "binmode", "open", and the "open"
	       pragma, open.

       tell FILEHANDLE
       tell    Returns the current position in bytes for FILEHANDLE, or -1 on
	       error.  FILEHANDLE may be an expression whose value gives the
	       name of the actual filehandle.  If FILEHANDLE is omitted,
	       assumes the file last read.

	       Note the in bytes: even if the filehandle has been set to
	       operate on characters (for example by using the
	       ":encoding(utf8)" open layer), tell() will return byte offsets,
	       not character offsets (because that would render seek() and
	       tell() rather slow).

	       The return value of tell() for the standard streams like the
	       STDIN depends on the operating system: it may return -1 or
	       something else.	tell() on pipes, fifos, and sockets usually
	       returns -1.

	       There is no "systell" function.	Use "sysseek(FH, 0, 1)" for
	       that.

	       Do not use tell() (or other buffered I/O operations) on a file
	       handle that has been manipulated by sysread(), syswrite() or
	       sysseek().  Those functions ignore the buffering, while tell()
	       does not.

       telldir DIRHANDLE
	       Returns the current position of the "readdir" routines on
	       DIRHANDLE.  Value may be given to "seekdir" to access a
	       particular location in a directory.  "telldir" has the same
	       caveats about possible directory compaction as the
	       corresponding system library routine.

       tie VARIABLE,CLASSNAME,LIST
	       This function binds a variable to a package class that will
	       provide the implementation for the variable.  VARIABLE is the
	       name of the variable to be enchanted.  CLASSNAME is the name of
	       a class implementing objects of correct type.  Any additional
	       arguments are passed to the "new" method of the class (meaning
	       "TIESCALAR", "TIEHANDLE", "TIEARRAY", or "TIEHASH").  Typically
	       these are arguments such as might be passed to the "dbm_open()"
	       function of C.  The object returned by the "new" method is also
	       returned by the "tie" function, which would be useful if you
	       want to access other methods in CLASSNAME.

	       Note that functions such as "keys" and "values" may return huge
	       lists when used on large objects, like DBM files.  You may
	       prefer to use the "each" function to iterate over such.
	       Example:

		   # print out history file offsets
		   use NDBM_File;
		   tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);
		   while (($key,$val) = each %HIST) {
		       print $key, ' = ', unpack('L',$val), "\n";
		   }
		   untie(%HIST);

	       A class implementing a hash should have the following methods:

		   TIEHASH classname, LIST
		   FETCH this, key
		   STORE this, key, value
		   DELETE this, key
		   CLEAR this
		   EXISTS this, key
		   FIRSTKEY this
		   NEXTKEY this, lastkey
		   SCALAR this
		   DESTROY this
		   UNTIE this

	       A class implementing an ordinary array should have the
	       following methods:

		   TIEARRAY classname, LIST
		   FETCH this, key
		   STORE this, key, value
		   FETCHSIZE this
		   STORESIZE this, count
		   CLEAR this
		   PUSH this, LIST
		   POP this
		   SHIFT this
		   UNSHIFT this, LIST
		   SPLICE this, offset, length, LIST
		   EXTEND this, count
		   DESTROY this
		   UNTIE this

	       A class implementing a file handle should have the following
	       methods:

		   TIEHANDLE classname, LIST
		   READ this, scalar, length, offset
		   READLINE this
		   GETC this
		   WRITE this, scalar, length, offset
		   PRINT this, LIST
		   PRINTF this, format, LIST
		   BINMODE this
		   EOF this
		   FILENO this
		   SEEK this, position, whence
		   TELL this
		   OPEN this, mode, LIST
		   CLOSE this
		   DESTROY this
		   UNTIE this

	       A class implementing a scalar should have the following
	       methods:

		   TIESCALAR classname, LIST
		   FETCH this,
		   STORE this, value
		   DESTROY this
		   UNTIE this

	       Not all methods indicated above need be implemented.  See
	       perltie, Tie::Hash, Tie::Array, Tie::Scalar, and Tie::Handle.

	       Unlike "dbmopen", the "tie" function will not use or require a
	       module for you--you need to do that explicitly yourself.	 See
	       DB_File or the Config module for interesting "tie"
	       implementations.

	       For further details see perltie, "tied VARIABLE".

       tied VARIABLE
	       Returns a reference to the object underlying VARIABLE (the same
	       value that was originally returned by the "tie" call that bound
	       the variable to a package.)  Returns the undefined value if
	       VARIABLE isn't tied to a package.

       time    Returns the number of non-leap seconds since whatever time the
	       system considers to be the epoch, suitable for feeding to
	       "gmtime" and "localtime". On most systems the epoch is 00:00:00
	       UTC, January 1, 1970; a prominent exception being Mac OS
	       Classic which uses 00:00:00, January 1, 1904 in the current
	       local time zone for its epoch.

	       For measuring time in better granularity than one second, you
	       may use either the Time::HiRes module (from CPAN, and starting
	       from Perl 5.8 part of the standard distribution), or if you
	       have gettimeofday(2), you may be able to use the "syscall"
	       interface of Perl.  See perlfaq8 for details.

	       For date and time processing look at the many related modules
	       on CPAN.	 For a comprehensive date and time representation look
	       at the DateTime module.

       times   Returns a four-element list giving the user and system times,
	       in seconds, for this process and the children of this process.

		   ($user,$system,$cuser,$csystem) = times;

	       In scalar context, "times" returns $user.

	       Note that times for children are included only after they
	       terminate.

       tr///   The transliteration operator.  Same as "y///".  See "Quote and
	       Quote-like Operators" in perlop.

       truncate FILEHANDLE,LENGTH
       truncate EXPR,LENGTH
	       Truncates the file opened on FILEHANDLE, or named by EXPR, to
	       the specified length.  Produces a fatal error if truncate isn't
	       implemented on your system.  Returns true if successful, the
	       undefined value otherwise.

	       The behavior is undefined if LENGTH is greater than the length
	       of the file.

	       The position in the file of FILEHANDLE is left unchanged.  You
	       may want to call seek before writing to the file.

       uc EXPR
       uc      Returns an uppercased version of EXPR.  This is the internal
	       function implementing the "\U" escape in double-quoted strings.
	       Respects current LC_CTYPE locale if "use locale" in force.  See
	       perllocale and perlunicode for more details about locale and
	       Unicode support.	 It does not attempt to do titlecase mapping
	       on initial letters.  See "ucfirst" for that.

	       If EXPR is omitted, uses $_.

       ucfirst EXPR
       ucfirst Returns the value of EXPR with the first character in uppercase
	       (titlecase in Unicode).	This is the internal function
	       implementing the "\u" escape in double-quoted strings.
	       Respects current LC_CTYPE locale if "use locale" in force.  See
	       perllocale and perlunicode for more details about locale and
	       Unicode support.

	       If EXPR is omitted, uses $_.

       umask EXPR
       umask   Sets the umask for the process to EXPR and returns the previous
	       value.  If EXPR is omitted, merely returns the current umask.

	       The Unix permission "rwxr-x---" is represented as three sets of
	       three bits, or three octal digits: 0750 (the leading 0
	       indicates octal and isn't one of the digits).  The "umask"
	       value is such a number representing disabled permissions bits.
	       The permission (or "mode") values you pass "mkdir" or "sysopen"
	       are modified by your umask, so even if you tell "sysopen" to
	       create a file with permissions 0777, if your umask is 0022 then
	       the file will actually be created with permissions 0755.	 If
	       your "umask" were 0027 (group can't write; others can't read,
	       write, or execute), then passing "sysopen" 0666 would create a
	       file with mode 0640 ("0666 &~ 027" is 0640).

	       Here's some advice: supply a creation mode of 0666 for regular
	       files (in "sysopen") and one of 0777 for directories (in
	       "mkdir") and executable files.  This gives users the freedom of
	       choice: if they want protected files, they might choose process
	       umasks of 022, 027, or even the particularly antisocial mask of
	       077.  Programs should rarely if ever make policy decisions
	       better left to the user.	 The exception to this is when writing
	       files that should be kept private: mail files, web browser
	       cookies, .rhosts files, and so on.

	       If umask(2) is not implemented on your system and you are
	       trying to restrict access for yourself (i.e., (EXPR & 0700) >
	       0), produces a fatal error at run time.	If umask(2) is not
	       implemented and you are not trying to restrict access for
	       yourself, returns "undef".

	       Remember that a umask is a number, usually given in octal; it
	       is not a string of octal digits.	 See also "oct", if all you
	       have is a string.

       undef EXPR
       undef   Undefines the value of EXPR, which must be an lvalue.  Use only
	       on a scalar value, an array (using "@"), a hash (using "%"), a
	       subroutine (using "&"), or a typeglob (using "*").  (Saying
	       "undef $hash{$key}" will probably not do what you expect on
	       most predefined variables or DBM list values, so don't do that;
	       see delete.)  Always returns the undefined value.  You can omit
	       the EXPR, in which case nothing is undefined, but you still get
	       an undefined value that you could, for instance, return from a
	       subroutine, assign to a variable or pass as a parameter.
	       Examples:

		   undef $foo;
		   undef $bar{'blurfl'};      # Compare to: delete $bar{'blurfl'};
		   undef @ary;
		   undef %hash;
		   undef &mysub;
		   undef *xyz;	     # destroys $xyz, @xyz, %xyz, &xyz, etc.
		   return (wantarray ? (undef, $errmsg) : undef) if $they_blew_it;
		   select undef, undef, undef, 0.25;
		   ($a, $b, undef, $c) = &foo;	     # Ignore third value returned

	       Note that this is a unary operator, not a list operator.

       unlink LIST
       unlink  Deletes a list of files.	 Returns the number of files
	       successfully deleted.

		   $cnt = unlink 'a', 'b', 'c';
		   unlink @goners;
		   unlink <*.bak>;

	       Note: "unlink" will not attempt to delete directories unless
	       you are superuser and the -U flag is supplied to Perl.  Even if
	       these conditions are met, be warned that unlinking a directory
	       can inflict damage on your filesystem.  Finally, using "unlink"
	       on directories is not supported on many operating systems.  Use
	       "rmdir" instead.

	       If LIST is omitted, uses $_.

       unpack TEMPLATE,EXPR
       unpack TEMPLATE
	       "unpack" does the reverse of "pack": it takes a string and
	       expands it out into a list of values.  (In scalar context, it
	       returns merely the first value produced.)

	       If EXPR is omitted, unpacks the $_ string.

	       The string is broken into chunks described by the TEMPLATE.
	       Each chunk is converted separately to a value.  Typically,
	       either the string is a result of "pack", or the characters of
	       the string represent a C structure of some kind.

	       The TEMPLATE has the same format as in the "pack" function.
	       Here's a subroutine that does substring:

		   sub substr {
		       my($what,$where,$howmuch) = @_;
		       unpack("x$where a$howmuch", $what);
		   }

	       and then there's

		   sub ordinal { unpack("W",$_[0]); } # same as ord()

	       In addition to fields allowed in pack(), you may prefix a field
	       with a %<number> to indicate that you want a <number>-bit
	       checksum of the items instead of the items themselves.  Default
	       is a 16-bit checksum.  Checksum is calculated by summing
	       numeric values of expanded values (for string fields the sum of
	       "ord($char)" is taken, for bit fields the sum of zeroes and
	       ones).

	       For example, the following computes the same number as the
	       System V sum program:

		   $checksum = do {
		       local $/;  # slurp!
		       unpack("%32W*",<>) % 65535;
		   };

	       The following efficiently counts the number of set bits in a
	       bit vector:

		   $setbits = unpack("%32b*", $selectmask);

	       The "p" and "P" formats should be used with care.  Since Perl
	       has no way of checking whether the value passed to "unpack()"
	       corresponds to a valid memory location, passing a pointer value
	       that's not known to be valid is likely to have disastrous
	       consequences.

	       If there are more pack codes or if the repeat count of a field
	       or a group is larger than what the remainder of the input
	       string allows, the result is not well defined: in some cases,
	       the repeat count is decreased, or "unpack()" will produce null
	       strings or zeroes, or terminate with an error. If the input
	       string is longer than one described by the TEMPLATE, the rest
	       is ignored.

	       See "pack" for more examples and notes.

       untie VARIABLE
	       Breaks the binding between a variable and a package.  (See
	       "tie".)	Has no effect if the variable is not tied.

       unshift ARRAY,LIST
	       Does the opposite of a "shift".	Or the opposite of a "push",
	       depending on how you look at it.	 Prepends list to the front of
	       the array, and returns the new number of elements in the array.

		   unshift(@ARGV, '-e') unless $ARGV[0] =~ /^-/;

	       Note the LIST is prepended whole, not one element at a time, so
	       the prepended elements stay in the same order.  Use "reverse"
	       to do the reverse.

       use Module VERSION LIST
       use Module VERSION
       use Module LIST
       use Module
       use VERSION
	       Imports some semantics into the current package from the named
	       module, generally by aliasing certain subroutine or variable
	       names into your package.	 It is exactly equivalent to

		   BEGIN { require Module; Module->import( LIST ); }

	       except that Module must be a bareword.

	       In the peculiar "use VERSION" form, VERSION may be either a
	       numeric argument such as 5.006, which will be compared to $],
	       or a literal of the form v5.6.1, which will be compared to $^V
	       (aka $PERL_VERSION).  A fatal error is produced if VERSION is
	       greater than the version of the current Perl interpreter; Perl
	       will not attempt to parse the rest of the file.	Compare with
	       "require", which can do a similar check at run time.
	       Symmetrically, "no VERSION" allows you to specify that you want
	       a version of perl older than the specified one.

	       Specifying VERSION as a literal of the form v5.6.1 should
	       generally be avoided, because it leads to misleading error
	       messages under earlier versions of Perl (that is, prior to
	       5.6.0) that do not support this syntax.	The equivalent numeric
	       version should be used instead.

		   use v5.6.1;	       # compile time version check
		   use 5.6.1;	       # ditto
		   use 5.006_001;      # ditto; preferred for backwards compatibility

	       This is often useful if you need to check the current Perl
	       version before "use"ing library modules that won't work with
	       older versions of Perl.	(We try not to do this more than we
	       have to.)

	       Also, if the specified perl version is greater than or equal to
	       5.9.5, "use VERSION" will also load the "feature" pragma and
	       enable all features available in the requested version.	See
	       feature.

	       The "BEGIN" forces the "require" and "import" to happen at
	       compile time.  The "require" makes sure the module is loaded
	       into memory if it hasn't been yet.  The "import" is not a
	       builtin--it's just an ordinary static method call into the
	       "Module" package to tell the module to import the list of
	       features back into the current package.	The module can
	       implement its "import" method any way it likes, though most
	       modules just choose to derive their "import" method via
	       inheritance from the "Exporter" class that is defined in the
	       "Exporter" module.  See Exporter.  If no "import" method can be
	       found then the call is skipped, even if there is an AUTOLOAD
	       method.

	       If you do not want to call the package's "import" method (for
	       instance, to stop your namespace from being altered),
	       explicitly supply the empty list:

		   use Module ();

	       That is exactly equivalent to

		   BEGIN { require Module }

	       If the VERSION argument is present between Module and LIST,
	       then the "use" will call the VERSION method in class Module
	       with the given version as an argument.  The default VERSION
	       method, inherited from the UNIVERSAL class, croaks if the given
	       version is larger than the value of the variable
	       $Module::VERSION.

	       Again, there is a distinction between omitting LIST ("import"
	       called with no arguments) and an explicit empty LIST "()"
	       ("import" not called).  Note that there is no comma after
	       VERSION!

	       Because this is a wide-open interface, pragmas (compiler
	       directives) are also implemented this way.  Currently
	       implemented pragmas are:

		   use constant;
		   use diagnostics;
		   use integer;
		   use sigtrap	qw(SEGV BUS);
		   use strict	qw(subs vars refs);
		   use subs	qw(afunc blurfl);
		   use warnings qw(all);
		   use sort	qw(stable _quicksort _mergesort);

	       Some of these pseudo-modules import semantics into the current
	       block scope (like "strict" or "integer", unlike ordinary
	       modules, which import symbols into the current package (which
	       are effective through the end of the file).

	       There's a corresponding "no" command that unimports meanings
	       imported by "use", i.e., it calls "unimport Module LIST"
	       instead of "import".  It behaves exactly as "import" does with
	       respect to VERSION, an omitted LIST, empty LIST, or no unimport
	       method being found.

		   no integer;
		   no strict 'refs';
		   no warnings;

	       See perlmodlib for a list of standard modules and pragmas.  See
	       perlrun for the "-M" and "-m" command-line options to perl that
	       give "use" functionality from the command-line.

       utime LIST
	       Changes the access and modification times on each file of a
	       list of files.  The first two elements of the list must be the
	       NUMERICAL access and modification times, in that order.
	       Returns the number of files successfully changed.  The inode
	       change time of each file is set to the current time.  For
	       example, this code has the same effect as the Unix touch(1)
	       command when the files already exist and belong to the user
	       running the program:

		   #!/usr/bin/perl
		   $atime = $mtime = time;
		   utime $atime, $mtime, @ARGV;

	       Since perl 5.7.2, if the first two elements of the list are
	       "undef", then the utime(2) function in the C library will be
	       called with a null second argument. On most systems, this will
	       set the file's access and modification times to the current
	       time (i.e. equivalent to the example above) and will even work
	       on other users' files where you have write permission:

		   utime undef, undef, @ARGV;

	       Under NFS this will use the time of the NFS server, not the
	       time of the local machine.  If there is a time synchronization
	       problem, the NFS server and local machine will have different
	       times.  The Unix touch(1) command will in fact normally use
	       this form instead of the one shown in the first example.

	       Note that only passing one of the first two elements as "undef"
	       will be equivalent of passing it as 0 and will not have the
	       same effect as described when they are both "undef".  This case
	       will also trigger an uninitialized warning.

	       On systems that support futimes, you might pass file handles
	       among the files.	 On systems that don't support futimes,
	       passing file handles produces a fatal error at run time.	 The
	       file handles must be passed as globs or references to be
	       recognized.  Barewords are considered file names.

       values HASH
	       Returns a list consisting of all the values of the named hash.
	       (In a scalar context, returns the number of values.)

	       The values are returned in an apparently random order.  The
	       actual random order is subject to change in future versions of
	       perl, but it is guaranteed to be the same order as either the
	       "keys" or "each" function would produce on the same
	       (unmodified) hash.  Since Perl 5.8.1 the ordering is different
	       even between different runs of Perl for security reasons (see
	       "Algorithmic Complexity Attacks" in perlsec).

	       As a side effect, calling values() resets the HASH's internal
	       iterator, see "each". (In particular, calling values() in void
	       context resets the iterator with no other overhead.)

	       Note that the values are not copied, which means modifying them
	       will modify the contents of the hash:

		   for (values %hash)	   { s/foo/bar/g }   # modifies %hash values
		   for (@hash{keys %hash}) { s/foo/bar/g }   # same

	       See also "keys", "each", and "sort".

       vec EXPR,OFFSET,BITS
	       Treats the string in EXPR as a bit vector made up of elements
	       of width BITS, and returns the value of the element specified
	       by OFFSET as an unsigned integer.  BITS therefore specifies the
	       number of bits that are reserved for each element in the bit
	       vector.	This must be a power of two from 1 to 32 (or 64, if
	       your platform supports that).

	       If BITS is 8, "elements" coincide with bytes of the input
	       string.

	       If BITS is 16 or more, bytes of the input string are grouped
	       into chunks of size BITS/8, and each group is converted to a
	       number as with pack()/unpack() with big-endian formats "n"/"N"
	       (and analogously for BITS==64).	See "pack" for details.

	       If bits is 4 or less, the string is broken into bytes, then the
	       bits of each byte are broken into 8/BITS groups.	 Bits of a
	       byte are numbered in a little-endian-ish way, as in 0x01, 0x02,
	       0x04, 0x08, 0x10, 0x20, 0x40, 0x80.  For example, breaking the
	       single input byte "chr(0x36)" into two groups gives a list
	       "(0x6, 0x3)"; breaking it into 4 groups gives "(0x2, 0x1, 0x3,
	       0x0)".

	       "vec" may also be assigned to, in which case parentheses are
	       needed to give the expression the correct precedence as in

		   vec($image, $max_x * $x + $y, 8) = 3;

	       If the selected element is outside the string, the value 0 is
	       returned.  If an element off the end of the string is written
	       to, Perl will first extend the string with sufficiently many
	       zero bytes.   It is an error to try to write off the beginning
	       of the string (i.e. negative OFFSET).

	       If the string happens to be encoded as UTF-8 internally (and
	       thus has the UTF8 flag set), this is ignored by "vec", and it
	       operates on the internal byte string, not the conceptual
	       character string, even if you only have characters with values
	       less than 256.

	       Strings created with "vec" can also be manipulated with the
	       logical operators "|", "&", "^", and "~".  These operators will
	       assume a bit vector operation is desired when both operands are
	       strings.	 See "Bitwise String Operators" in perlop.

	       The following code will build up an ASCII string saying
	       'PerlPerlPerl'.	The comments show the string after each step.
	       Note that this code works in the same way on big-endian or
	       little-endian machines.

		   my $foo = '';
		   vec($foo,  0, 32) = 0x5065726C;     # 'Perl'

		   # $foo eq "Perl" eq "\x50\x65\x72\x6C", 32 bits
		   print vec($foo, 0, 8);	       # prints 80 == 0x50 == ord('P')

		   vec($foo,  2, 16) = 0x5065;	       # 'PerlPe'
		   vec($foo,  3, 16) = 0x726C;	       # 'PerlPerl'
		   vec($foo,  8,  8) = 0x50;	       # 'PerlPerlP'
		   vec($foo,  9,  8) = 0x65;	       # 'PerlPerlPe'
		   vec($foo, 20,  4) = 2;	       # 'PerlPerlPe'	. "\x02"
		   vec($foo, 21,  4) = 7;	       # 'PerlPerlPer'
						       # 'r' is "\x72"
		   vec($foo, 45,  2) = 3;	       # 'PerlPerlPer'	. "\x0c"
		   vec($foo, 93,  1) = 1;	       # 'PerlPerlPer'	. "\x2c"
		   vec($foo, 94,  1) = 1;	       # 'PerlPerlPerl'
						       # 'l' is "\x6c"

	       To transform a bit vector into a string or list of 0's and 1's,
	       use these:

		   $bits = unpack("b*", $vector);
		   @bits = split(//, unpack("b*", $vector));

	       If you know the exact length in bits, it can be used in place
	       of the "*".

	       Here is an example to illustrate how the bits actually fall in
	       place:

		   #!/usr/bin/perl -wl

		   print <<'EOT';
						     0	       1	 2	   3
				      unpack("V",$_) 01234567890123456789012345678901
		   ------------------------------------------------------------------
		   EOT

		   for $w (0..3) {
		       $width = 2**$w;
		       for ($shift=0; $shift < $width; ++$shift) {
			   for ($off=0; $off < 32/$width; ++$off) {
			       $str = pack("B*", "0"x32);
			       $bits = (1<<$shift);
			       vec($str, $off, $width) = $bits;
			       $res = unpack("b*",$str);
			       $val = unpack("V", $str);
			       write;
			   }
		       }
		   }

		   format STDOUT =
		   vec($_,@#,@#) = @<< == @######### @>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
		   $off, $width, $bits, $val, $res
		   .
		   __END__

	       Regardless of the machine architecture on which it is run, the
	       above example should print the following table:

						     0	       1	 2	   3
				      unpack("V",$_) 01234567890123456789012345678901
		   ------------------------------------------------------------------
		   vec($_, 0, 1) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 1) = 1   ==	   2 01000000000000000000000000000000
		   vec($_, 2, 1) = 1   ==	   4 00100000000000000000000000000000
		   vec($_, 3, 1) = 1   ==	   8 00010000000000000000000000000000
		   vec($_, 4, 1) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 5, 1) = 1   ==	  32 00000100000000000000000000000000
		   vec($_, 6, 1) = 1   ==	  64 00000010000000000000000000000000
		   vec($_, 7, 1) = 1   ==	 128 00000001000000000000000000000000
		   vec($_, 8, 1) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 9, 1) = 1   ==	 512 00000000010000000000000000000000
		   vec($_,10, 1) = 1   ==	1024 00000000001000000000000000000000
		   vec($_,11, 1) = 1   ==	2048 00000000000100000000000000000000
		   vec($_,12, 1) = 1   ==	4096 00000000000010000000000000000000
		   vec($_,13, 1) = 1   ==	8192 00000000000001000000000000000000
		   vec($_,14, 1) = 1   ==      16384 00000000000000100000000000000000
		   vec($_,15, 1) = 1   ==      32768 00000000000000010000000000000000
		   vec($_,16, 1) = 1   ==      65536 00000000000000001000000000000000
		   vec($_,17, 1) = 1   ==     131072 00000000000000000100000000000000
		   vec($_,18, 1) = 1   ==     262144 00000000000000000010000000000000
		   vec($_,19, 1) = 1   ==     524288 00000000000000000001000000000000
		   vec($_,20, 1) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_,21, 1) = 1   ==    2097152 00000000000000000000010000000000
		   vec($_,22, 1) = 1   ==    4194304 00000000000000000000001000000000
		   vec($_,23, 1) = 1   ==    8388608 00000000000000000000000100000000
		   vec($_,24, 1) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_,25, 1) = 1   ==   33554432 00000000000000000000000001000000
		   vec($_,26, 1) = 1   ==   67108864 00000000000000000000000000100000
		   vec($_,27, 1) = 1   ==  134217728 00000000000000000000000000010000
		   vec($_,28, 1) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_,29, 1) = 1   ==  536870912 00000000000000000000000000000100
		   vec($_,30, 1) = 1   == 1073741824 00000000000000000000000000000010
		   vec($_,31, 1) = 1   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 2) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 2) = 1   ==	   4 00100000000000000000000000000000
		   vec($_, 2, 2) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 3, 2) = 1   ==	  64 00000010000000000000000000000000
		   vec($_, 4, 2) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 5, 2) = 1   ==	1024 00000000001000000000000000000000
		   vec($_, 6, 2) = 1   ==	4096 00000000000010000000000000000000
		   vec($_, 7, 2) = 1   ==      16384 00000000000000100000000000000000
		   vec($_, 8, 2) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 9, 2) = 1   ==     262144 00000000000000000010000000000000
		   vec($_,10, 2) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_,11, 2) = 1   ==    4194304 00000000000000000000001000000000
		   vec($_,12, 2) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_,13, 2) = 1   ==   67108864 00000000000000000000000000100000
		   vec($_,14, 2) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_,15, 2) = 1   == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 2) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 2) = 2   ==	   8 00010000000000000000000000000000
		   vec($_, 2, 2) = 2   ==	  32 00000100000000000000000000000000
		   vec($_, 3, 2) = 2   ==	 128 00000001000000000000000000000000
		   vec($_, 4, 2) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 5, 2) = 2   ==	2048 00000000000100000000000000000000
		   vec($_, 6, 2) = 2   ==	8192 00000000000001000000000000000000
		   vec($_, 7, 2) = 2   ==      32768 00000000000000010000000000000000
		   vec($_, 8, 2) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 9, 2) = 2   ==     524288 00000000000000000001000000000000
		   vec($_,10, 2) = 2   ==    2097152 00000000000000000000010000000000
		   vec($_,11, 2) = 2   ==    8388608 00000000000000000000000100000000
		   vec($_,12, 2) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_,13, 2) = 2   ==  134217728 00000000000000000000000000010000
		   vec($_,14, 2) = 2   ==  536870912 00000000000000000000000000000100
		   vec($_,15, 2) = 2   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 4) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 4) = 1   ==	  16 00001000000000000000000000000000
		   vec($_, 2, 4) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 3, 4) = 1   ==	4096 00000000000010000000000000000000
		   vec($_, 4, 4) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 5, 4) = 1   ==    1048576 00000000000000000000100000000000
		   vec($_, 6, 4) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_, 7, 4) = 1   ==  268435456 00000000000000000000000000001000
		   vec($_, 0, 4) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 4) = 2   ==	  32 00000100000000000000000000000000
		   vec($_, 2, 4) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 3, 4) = 2   ==	8192 00000000000001000000000000000000
		   vec($_, 4, 4) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 5, 4) = 2   ==    2097152 00000000000000000000010000000000
		   vec($_, 6, 4) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_, 7, 4) = 2   ==  536870912 00000000000000000000000000000100
		   vec($_, 0, 4) = 4   ==	   4 00100000000000000000000000000000
		   vec($_, 1, 4) = 4   ==	  64 00000010000000000000000000000000
		   vec($_, 2, 4) = 4   ==	1024 00000000001000000000000000000000
		   vec($_, 3, 4) = 4   ==      16384 00000000000000100000000000000000
		   vec($_, 4, 4) = 4   ==     262144 00000000000000000010000000000000
		   vec($_, 5, 4) = 4   ==    4194304 00000000000000000000001000000000
		   vec($_, 6, 4) = 4   ==   67108864 00000000000000000000000000100000
		   vec($_, 7, 4) = 4   == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 4) = 8   ==	   8 00010000000000000000000000000000
		   vec($_, 1, 4) = 8   ==	 128 00000001000000000000000000000000
		   vec($_, 2, 4) = 8   ==	2048 00000000000100000000000000000000
		   vec($_, 3, 4) = 8   ==      32768 00000000000000010000000000000000
		   vec($_, 4, 4) = 8   ==     524288 00000000000000000001000000000000
		   vec($_, 5, 4) = 8   ==    8388608 00000000000000000000000100000000
		   vec($_, 6, 4) = 8   ==  134217728 00000000000000000000000000010000
		   vec($_, 7, 4) = 8   == 2147483648 00000000000000000000000000000001
		   vec($_, 0, 8) = 1   ==	   1 10000000000000000000000000000000
		   vec($_, 1, 8) = 1   ==	 256 00000000100000000000000000000000
		   vec($_, 2, 8) = 1   ==      65536 00000000000000001000000000000000
		   vec($_, 3, 8) = 1   ==   16777216 00000000000000000000000010000000
		   vec($_, 0, 8) = 2   ==	   2 01000000000000000000000000000000
		   vec($_, 1, 8) = 2   ==	 512 00000000010000000000000000000000
		   vec($_, 2, 8) = 2   ==     131072 00000000000000000100000000000000
		   vec($_, 3, 8) = 2   ==   33554432 00000000000000000000000001000000
		   vec($_, 0, 8) = 4   ==	   4 00100000000000000000000000000000
		   vec($_, 1, 8) = 4   ==	1024 00000000001000000000000000000000
		   vec($_, 2, 8) = 4   ==     262144 00000000000000000010000000000000
		   vec($_, 3, 8) = 4   ==   67108864 00000000000000000000000000100000
		   vec($_, 0, 8) = 8   ==	   8 00010000000000000000000000000000
		   vec($_, 1, 8) = 8   ==	2048 00000000000100000000000000000000
		   vec($_, 2, 8) = 8   ==     524288 00000000000000000001000000000000
		   vec($_, 3, 8) = 8   ==  134217728 00000000000000000000000000010000
		   vec($_, 0, 8) = 16  ==	  16 00001000000000000000000000000000
		   vec($_, 1, 8) = 16  ==	4096 00000000000010000000000000000000
		   vec($_, 2, 8) = 16  ==    1048576 00000000000000000000100000000000
		   vec($_, 3, 8) = 16  ==  268435456 00000000000000000000000000001000
		   vec($_, 0, 8) = 32  ==	  32 00000100000000000000000000000000
		   vec($_, 1, 8) = 32  ==	8192 00000000000001000000000000000000
		   vec($_, 2, 8) = 32  ==    2097152 00000000000000000000010000000000
		   vec($_, 3, 8) = 32  ==  536870912 00000000000000000000000000000100
		   vec($_, 0, 8) = 64  ==	  64 00000010000000000000000000000000
		   vec($_, 1, 8) = 64  ==      16384 00000000000000100000000000000000
		   vec($_, 2, 8) = 64  ==    4194304 00000000000000000000001000000000
		   vec($_, 3, 8) = 64  == 1073741824 00000000000000000000000000000010
		   vec($_, 0, 8) = 128 ==	 128 00000001000000000000000000000000
		   vec($_, 1, 8) = 128 ==      32768 00000000000000010000000000000000
		   vec($_, 2, 8) = 128 ==    8388608 00000000000000000000000100000000
		   vec($_, 3, 8) = 128 == 2147483648 00000000000000000000000000000001

       wait    Behaves like the wait(2) system call on your system: it waits
	       for a child process to terminate and returns the pid of the
	       deceased process, or "-1" if there are no child processes.  The
	       status is returned in $?	 and "${^CHILD_ERROR_NATIVE}".	Note
	       that a return value of "-1" could mean that child processes are
	       being automatically reaped, as described in perlipc.

       waitpid PID,FLAGS
	       Waits for a particular child process to terminate and returns
	       the pid of the deceased process, or "-1" if there is no such
	       child process.  On some systems, a value of 0 indicates that
	       there are processes still running.  The status is returned in
	       $? and "${^CHILD_ERROR_NATIVE}".	 If you say

		   use POSIX ":sys_wait_h";
		   #...
		   do {
		       $kid = waitpid(-1, WNOHANG);
		   } while $kid > 0;

	       then you can do a non-blocking wait for all pending zombie
	       processes.  Non-blocking wait is available on machines
	       supporting either the waitpid(2) or wait4(2) system calls.
	       However, waiting for a particular pid with FLAGS of 0 is
	       implemented everywhere.	(Perl emulates the system call by
	       remembering the status values of processes that have exited but
	       have not been harvested by the Perl script yet.)

	       Note that on some systems, a return value of "-1" could mean
	       that child processes are being automatically reaped.  See
	       perlipc for details, and for other examples.

       wantarray
	       Returns true if the context of the currently executing
	       subroutine or "eval" is looking for a list value.  Returns
	       false if the context is looking for a scalar.  Returns the
	       undefined value if the context is looking for no value (void
	       context).

		   return unless defined wantarray;    # don't bother doing more
		   my @a = complex_calculation();
		   return wantarray ? @a : "@a";

	       "wantarray()"'s result is unspecified in the top level of a
	       file, in a "BEGIN", "UNITCHECK", "CHECK", "INIT" or "END"
	       block, or in a "DESTROY" method.

	       This function should have been named wantlist() instead.

       warn LIST
	       Prints the value of LIST to STDERR.  If the last element of
	       LIST does not end in a newline, it appends the same file/line
	       number text as "die" does.

	       If LIST is empty and $@ already contains a value (typically
	       from a previous eval) that value is used after appending
	       "\t...caught" to $@.  This is useful for staying almost, but
	       not entirely similar to "die".

	       If $@ is empty then the string "Warning: Something's wrong" is
	       used.

	       No message is printed if there is a $SIG{__WARN__} handler
	       installed.  It is the handler's responsibility to deal with the
	       message as it sees fit (like, for instance, converting it into
	       a "die").  Most handlers must therefore make arrangements to
	       actually display the warnings that they are not prepared to
	       deal with, by calling "warn" again in the handler.  Note that
	       this is quite safe and will not produce an endless loop, since
	       "__WARN__" hooks are not called from inside one.

	       You will find this behavior is slightly different from that of
	       $SIG{__DIE__} handlers (which don't suppress the error text,
	       but can instead call "die" again to change it).

	       Using a "__WARN__" handler provides a powerful way to silence
	       all warnings (even the so-called mandatory ones).  An example:

		   # wipe out *all* compile-time warnings
		   BEGIN { $SIG{'__WARN__'} = sub { warn $_[0] if $DOWARN } }
		   my $foo = 10;
		   my $foo = 20;	  # no warning about duplicate my $foo,
					  # but hey, you asked for it!
		   # no compile-time or run-time warnings before here
		   $DOWARN = 1;

		   # run-time warnings enabled after here
		   warn "\$foo is alive and $foo!";	# does show up

	       See perlvar for details on setting %SIG entries, and for more
	       examples.  See the Carp module for other kinds of warnings
	       using its carp() and cluck() functions.

       write FILEHANDLE
       write EXPR
       write   Writes a formatted record (possibly multi-line) to the
	       specified FILEHANDLE, using the format associated with that
	       file.  By default the format for a file is the one having the
	       same name as the filehandle, but the format for the current
	       output channel (see the "select" function) may be set
	       explicitly by assigning the name of the format to the $~
	       variable.

	       Top of form processing is handled automatically:	 if there is
	       insufficient room on the current page for the formatted record,
	       the page is advanced by writing a form feed, a special top-of-
	       page format is used to format the new page header, and then the
	       record is written.  By default the top-of-page format is the
	       name of the filehandle with "_TOP" appended, but it may be
	       dynamically set to the format of your choice by assigning the
	       name to the $^ variable while the filehandle is selected.  The
	       number of lines remaining on the current page is in variable
	       "$-", which can be set to 0 to force a new page.

	       If FILEHANDLE is unspecified, output goes to the current
	       default output channel, which starts out as STDOUT but may be
	       changed by the "select" operator.  If the FILEHANDLE is an
	       EXPR, then the expression is evaluated and the resulting string
	       is used to look up the name of the FILEHANDLE at run time.  For
	       more on formats, see perlform.

	       Note that write is not the opposite of "read".  Unfortunately.

       y///    The transliteration operator.  Same as "tr///".	See "Quote and
	       Quote-like Operators" in perlop.

perl v5.10.1			  2009-08-12			   PERLFUNC(1)
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