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PERL571DELTA(1)	       Perl Programmers Reference Guide	       PERL571DELTA(1)

       perl571delta - what's new for perl v5.7.1

       This document describes differences between the 5.7.0 release and the
       5.7.1 release.

       (To view the differences between the 5.6.0 release and the 5.7.0
       release, see perl570delta.)

Security Vulnerability Closed
       (This change was already made in 5.7.0 but bears repeating here.)

       A potential security vulnerability in the optional suidperl component
       of Perl was identified in August 2000.  suidperl is neither built nor
       installed by default.  As of April 2001 the only known vulnerable
       platform is Linux, most likely all Linux distributions.	CERT and
       various vendors and distributors have been alerted about the
       vulnerability.  See for
       more information.

       The problem was caused by Perl trying to report a suspected security
       exploit attempt using an external program, /bin/mail.  On Linux
       platforms the /bin/mail program had an undocumented feature which when
       combined with suidperl gave access to a root shell, resulting in a
       serious compromise instead of reporting the exploit attempt.  If you
       don't have /bin/mail, or if you have 'safe setuid scripts', or if
       suidperl is not installed, you are safe.

       The exploit attempt reporting feature has been completely removed from
       all the Perl 5.7 releases (and will be gone also from the maintenance
       release 5.6.1), so that particular vulnerability isn't there anymore.
       However, further security vulnerabilities are, unfortunately, always
       possible.  The suidperl code is being reviewed and if deemed too risky
       to continue to be supported, it may be completely removed from future
       releases.  In any case, suidperl should only be used by security
       experts who know exactly what they are doing and why they are using
       suidperl instead of some other solution such as sudo ( see ).

Incompatible Changes
       ·   Although "you shouldn't do that", it was possible to write code
	   that depends on Perl's hashed key order (Data::Dumper does this).
	   The new algorithm "One-at-a-Time" produces a different hashed key
	   order.  More details are in "Performance Enhancements".

       ·   The list of filenames from glob() (or <...>) is now by default
	   sorted alphabetically to be csh-compliant.  (bsd_glob() does still
	   sort platform natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is

Core Enhancements
   AUTOLOAD Is Now Lvaluable
       AUTOLOAD is now lvaluable, meaning that you can add the :lvalue
       attribute to AUTOLOAD subroutines and you can assign to the AUTOLOAD
       return value.

   PerlIO is Now The Default
       ·   IO is now by default done via PerlIO rather than system's "stdio".
	   PerlIO allows "layers" to be "pushed" onto a file handle to alter
	   the handle's behaviour.  Layers can be specified at open time via
	   3-arg form of open:

	      open($fh,'>:crlf :utf8', $path) || ...

	   or on already opened handles via extended "binmode":


	   The built-in layers are: unix (low level read/write), stdio (as in
	   previous Perls), perlio (re-implementation of stdio buffering in a
	   portable manner), crlf (does CRLF <=> "\n" translation as on Win32,
	   but available on any platform).  A mmap layer may be available if
	   platform supports it (mostly Unixes).

	   Layers to be applied by default may be specified via the 'open'

	   See "Installation and Configuration Improvements" for the effects
	   of PerlIO on your architecture name.

       ·   File handles can be marked as accepting Perl's internal encoding of
	   Unicode (UTF-8 or UTF-EBCDIC depending on platform) by a pseudo
	   layer ":utf8" :


	   Note for EBCDIC users: the pseudo layer ":utf8" is erroneously
	   named for you since it's not UTF-8 what you will be getting but
	   instead UTF-EBCDIC.	See perlunicode, utf8, and for more information.
	   In future releases this naming may change.

       ·   File handles can translate character encodings from/to Perl's
	   internal Unicode form on read/write via the ":encoding()" layer.

       ·   File handles can be opened to "in memory" files held in Perl
	   scalars via:

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

       ·   Anonymous temporary files are available without need to 'use
	   FileHandle' or other module via

	      open($fh,"+>", undef) || ...

	   That is a literal undef, not an undefined value.

       ·   The list form of "open" is now implemented for pipes (at least on

	      open($fh,"-|", 'cat', '/etc/motd')

	   creates a pipe, and runs the equivalent of exec('cat', '/etc/motd')
	   in the child process.

       ·   The following builtin functions are now overridable: chop(),
	   chomp(), each(), keys(), pop(), push(), shift(), splice(),

       ·   Formats now support zero-padded decimal fields.

       ·   Perl now tries internally to use integer values in numeric
	   conversions and basic arithmetics (+ - * /) if the arguments are
	   integers, and tries also to keep the results stored internally as
	   integers.  This change leads into often slightly faster and always
	   less lossy arithmetics. (Previously Perl always preferred floating
	   point numbers in its math.)

       ·   The printf() and sprintf() now support parameter reordering using
	   the "%\d+\$" and "*\d+\$" syntaxes.	For example

	       print "%2\$s %1\$s\n", "foo", "bar";

	   will print "bar foo\n"; This feature helps in writing
	   internationalised software.

       ·   Unicode in general should be now much more usable.  Unicode can be
	   used in hash keys, Unicode in regular expressions should work now,
	   Unicode in tr/// should work now (though tr/// seems to be a
	   particularly tricky to get right, so you have been warned)

       ·   The Unicode Character Database coming with Perl has been upgraded
	   to Unicode 3.1.  For more information, see
	   , and

	   For developers interested in enhancing Perl's Unicode capabilities:
	   almost all the UCD files are included with the Perl distribution in
	   the lib/unicode subdirectory.  The most notable omission, for space
	   considerations, is the Unihan database.

       ·   The Unicode character classes \p{Blank} and \p{SpacePerl} have been
	   added.  "Blank" is like C isblank(), that is, it contains only
	   "horizontal whitespace" (the space character is, the newline
	   isn't), and the "SpacePerl" is the Unicode equivalent of "\s"
	   (\p{Space} isn't, since that includes the vertical tabulator
	   character, whereas "\s" doesn't.)

   Signals Are Now Safe
       Perl used to be fragile in that signals arriving at inopportune moments
       could corrupt Perl's internal state.

Modules and Pragmata
   New Modules
       ·   B::Concise, by Stephen McCamant, is a new compiler backend for
	   walking the Perl syntax tree, printing concise info about ops.  The
	   output is highly customisable.

	   See B::Concise for more information.

       ·   Class::ISA, by Sean Burke, for reporting the search path for a
	   class's ISA tree, has been added.

	   See Class::ISA for more information.

       ·   Cwd has now a split personality: if possible, an extension is used,
	   (this will hopefully be both faster and more secure and robust) but
	   if not possible, the familiar Perl library implementation is used.

       ·   Digest, a frontend module for calculating digests (checksums), from
	   Gisle Aas, has been added.

	   See Digest for more information.

       ·   Digest::MD5 for calculating MD5 digests (checksums), by Gisle Aas,
	   has been added.

	       use Digest::MD5 'md5_hex';

	       $digest = md5_hex("Thirsty Camel");

	       print $digest, "\n"; # 01d19d9d2045e005c3f1b80e8b164de1

	   NOTE: the MD5 backward compatibility module is deliberately not
	   included since its use is discouraged.

	   See Digest::MD5 for more information.

       ·   Encode, by Nick Ing-Simmons, provides a mechanism to translate
	   between different character encodings.  Support for Unicode,
	   ISO-8859-*, ASCII, CP*, KOI8-R, and three variants of EBCDIC are
	   compiled in to the module.  Several other encodings (like Japanese,
	   Chinese, and MacIntosh encodings) are included and will be loaded
	   at runtime.

	   Any encoding supported by Encode module is also available to the
	   ":encoding()" layer if PerlIO is used.

	   See Encode for more information.

       ·   Filter::Simple is an easy-to-use frontend to Filter::Util::Call,
	   from Damian Conway.

	       # in

	       package MyFilter;

	       use Filter::Simple sub {
		   while (my ($from, $to) = splice @_, 0, 2) {


	       # in user's code:

	       use MyFilter qr/red/ => 'green';

	       print "red\n";	# this code is filtered, will print "green\n"
	       print "bored\n"; # this code is filtered, will print "bogreen\n"

	       no MyFilter;

	       print "red\n";	# this code is not filtered, will print "red\n"

	   See Filter::Simple for more information.

       ·   Filter::Util::Call, by Paul Marquess, provides you with the
	   framework to write Source Filters in Perl.  For most uses the
	   frontend Filter::Simple is to be preferred.	See Filter::Util::Call
	   for more information.

       ·   Locale::Constants, Locale::Country, Locale::Currency, and
	   Locale::Language, from Neil Bowers, have been added.	 They provide
	   the codes for various locale standards, such as "fr" for France,
	   "usd" for US Dollar, and "jp" for Japanese.

	       use Locale::Country;

	       $country = code2country('jp');		    # $country gets 'Japan'
	       $code	= country2code('Norway');	    # $code gets 'no'

	   See Locale::Constants, Locale::Country, Locale::Currency, and
	   Locale::Language for more information.

       ·   MIME::Base64, by Gisle Aas, allows you to encode data in base64.

	       use MIME::Base64;

	       $encoded = encode_base64('Aladdin:open sesame');
	       $decoded = decode_base64($encoded);

	       print $encoded, "\n"; # "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="

	   See MIME::Base64 for more information.

       ·   MIME::QuotedPrint, by Gisle Aas, allows you to encode data in
	   quoted-printable encoding.

	       use MIME::QuotedPrint;

	       $encoded = encode_qp("Smiley in Unicode: \x{263a}");
	       $decoded = decode_qp($encoded);

	       print $encoded, "\n"; # "Smiley in Unicode: =263A"

	   MIME::QuotedPrint has been enhanced to provide the basic methods
	   necessary to use it with PerlIO::Via as in :

	       use MIME::QuotedPrint;

	   See MIME::QuotedPrint for more information.

       ·   PerlIO::Scalar, by Nick Ing-Simmons, provides the implementation of
	   IO to "in memory" Perl scalars as discussed above.  It also serves
	   as an example of a loadable layer.  Other future possibilities
	   include PerlIO::Array and PerlIO::Code.  See PerlIO::Scalar for
	   more information.

       ·   PerlIO::Via, by Nick Ing-Simmons, acts as a PerlIO layer and wraps
	   PerlIO layer functionality provided by a class (typically
	   implemented in perl code).

	       use MIME::QuotedPrint;

	   This will automatically convert everything output to $fh to Quoted-
	   Printable.  See PerlIO::Via for more information.

       ·   Pod::Text::Overstrike, by Joe Smith, has been added.	 It converts
	   POD data to formatted overstrike text.  See Pod::Text::Overstrike
	   for more information.

       ·   Switch from Damian Conway has been added.  Just by saying

	       use Switch;

	   you have "switch" and "case" available in Perl.

	       use Switch;

	       switch ($val) {

			   case 1	   { print "number 1" }
			   case "a"	   { print "string a" }
			   case [1..10,42] { print "number in list" }
			   case (@array)   { print "number in list" }
			   case /\w+/	   { print "pattern" }
			   case qr/\w+/	   { print "pattern" }
			   case (%hash)	   { print "entry in hash" }
			   case (\%hash)   { print "entry in hash" }
			   case (\&sub)	   { print "arg to subroutine" }
			   else		   { print "previous case not true" }

	   See Switch for more information.

       ·   Text::Balanced from Damian Conway has been added, for extracting
	   delimited text sequences from strings.

	       use Text::Balanced 'extract_delimited';

	       ($a, $b) = extract_delimited("'never say never', he never said", "'", '');

	   $a will be "'never say never'", $b will be ', he never said'.

	   In addition to extract_delimited() there are also
	   extract_bracketed(), extract_quotelike(), extract_codeblock(),
	   extract_variable(), extract_tagged(), extract_multiple(),
	   gen_delimited_pat(), and gen_extract_tagged().  With these you can
	   implement rather advanced parsing algorithms.  See Text::Balanced
	   for more information.

       ·   Tie::RefHash::Nestable, by Edward Avis, allows storing hash
	   references (unlike the standard Tie::RefHash)  The module is
	   contained within Tie::RefHash.

       ·   XS::Typemap, by Tim Jenness, is a test extension that exercises XS
	   typemaps.  Nothing gets installed but for extension writers the
	   code is worth studying.

   Updated And Improved Modules and Pragmata
       ·   B::Deparse should be now more robust.  It still far from providing
	   a full round trip for any random piece of Perl code, though, and is
	   under active development: expect more robustness in 5.7.2.

       ·   Class::Struct can now define the classes in compile time.

       ·   Math::BigFloat has undergone much fixing, and in addition the
	   fmod() function now supports modulus operations.

	   ( The fixed Math::BigFloat module is also available in CPAN for
	   those who can't upgrade their Perl: )

       ·   Devel::Peek now has an interface for the Perl memory statistics
	   (this works only if you are using perl's malloc, and if you have
	   compiled with debugging).

       ·   IO::Socket has now atmark() method, which returns true if the
	   socket is positioned at the out-of-band mark.  The method is also
	   exportable as a sockatmark() function.

       ·   IO::Socket::INET has support for ReusePort option (if your platform
	   supports it).  The Reuse option now has an alias, ReuseAddr.	 For
	   clarity you may want to prefer ReuseAddr.

       ·   Net::Ping has been enhanced.	 There is now "external" protocol
	   which uses Net::Ping::External module which runs external ping(1)
	   and parses the output.  An alpha version of Net::Ping::External is
	   available in CPAN and in 5.7.2 the Net::Ping::External may be
	   integrated to Perl.

       ·   The "open" pragma allows layers other than ":raw" and ":crlf" when
	   using PerlIO.

       ·   POSIX::sigaction() is now much more flexible and robust.  You can
	   now install coderef handlers, 'DEFAULT', and 'IGNORE' handlers,
	   installing new handlers was not atomic.

       ·   The Test module has been significantly enhanced.  Its use is
	   greatly recommended for module writers.

       ·   The utf8:: name space (as in the pragma) provides various Perl-
	   callable functions to provide low level access to Perl's internal
	   Unicode representation.  At the moment only length() has been

       The following modules have been upgraded from the versions at CPAN:
       CPAN, CGI, DB_File, File::Temp, Getopt::Long, Pod::Man, Pod::Text,
       Storable, Text-Tabs+Wrap.

Performance Enhancements
       ·   Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm ( ).  This algorithm is
	   reasonably fast while producing a much better spread of values than
	   the old hashing algorithm (originally by Chris Torek, later tweaked
	   by Ilya Zakharevich).  Hash values output from the algorithm on a
	   hash of all 3-char printable ASCII keys comes much closer to
	   passing the DIEHARD random number generation tests.	According to
	   perlbench, this change has not affected the overall speed of Perl.

       ·   unshift() should now be noticeably faster.

Utility Changes
       ·   h2xs now produces template README.

       ·   s2p has been completely rewritten in Perl.  (It is in fact a full
	   implementation of sed in Perl.)

       ·   xsubpp now supports OUT keyword.

New Documentation
       Internal replacements for standard C library functions.	(Interesting
       only for extension writers and Perl core hackers.)

       Internals of PerlIO with layers.

       Documentation on compiling Perl on AIX has been added.  AIX has several
       different C compilers and getting the right patch level is essential.
       On install README.aix will be installed as perlaix.

       Documentation on compiling Perl on the POSIX-BC platform (an EBCDIC
       mainframe environment) has been added.

       This was formerly known as README.posix-bc but the name was considered
       to be too confusing (it has nothing to do with the POSIX module or the
       POSIX standard).	 On install README.bs2000 will be installed as

       In perl 5.7.1 (and in the 5.6.1) the MacPerl sources have been
       synchronised with the standard Perl sources.  To compile MacPerl some
       additional steps are required, and this file documents those steps.  On
       install README.macos will be installed as perlmacos.

       The README.mpeix has been podified, which means that this information
       about compiling and using Perl on the MPE/iX miniframe platform will be
       installed as perlmpeix.

       README.solaris has been created and Solaris wisdom from elsewhere in
       the Perl documentation has been collected there.	 On install
       README.solaris will be installed as perlsolaris.

       The README.vos has been podified, which means that this information
       about compiling and using Perl on the Stratus VOS miniframe platform
       will be installed as perlvos.

       Documentation on how to use the Perl source repository has been added.

Installation and Configuration Improvements
       ·   Because PerlIO is now the default on most platforms, "-perlio"
	   doesn't get appended to the $Config{archname} (also known as $^O)
	   anymore.  Instead, if you explicitly choose not to use perlio
	   (Configure command line option -Uuseperlio), you will get "-stdio"

       ·   Another change related to the architecture name is that "-64all"
	   (-Duse64bitall, or "maximally 64-bit") is appended only if your
	   pointers are 64 bits wide.  (To be exact, the use64bitall is

       ·   APPLLIB_EXP, a less-know configuration-time definition, has been
	   documented.	It can be used to prepend site-specific directories to
	   Perl's default search path (@INC), see INSTALL for information.

       ·   Building Berkeley DB3 for compatibility modes for DB, NDBM, and
	   ODBM has been documented in INSTALL.

       ·   If you are on IRIX or Tru64 platforms, new profiling/debugging
	   options have been added, see perlhack for more information about
	   pixie and Third Degree.

   New Or Improved Platforms
       For the list of platforms known to support Perl, see "Supported
       Platforms" in perlport.

       ·   AIX dynamic loading should be now better supported.

       ·   After a long pause, AmigaOS has been verified to be happy with

       ·   EBCDIC platforms (z/OS, also known as OS/390, POSIX-BC, and VM/ESA)
	   have been regained.	Many test suite tests still fail and the co-
	   existence of Unicode and EBCDIC isn't quite settled, but the
	   situation is much better than with Perl 5.6.	 See perlos390,
	   perlbs2000 (for POSIX-BC), and perlvmesa for more information.

       ·   Building perl with -Duseithreads or -Duse5005threads now works
	   under HP-UX 10.20 (previously it only worked under 10.30 or later).
	   You will need a thread library package installed. See README.hpux.

       ·   Mac OS Classic (MacPerl has of course been available since perl
	   5.004 but now the source code bases of standard Perl and MacPerl
	   have been synchronised)

       ·   NCR MP-RAS is now supported.

       ·   NonStop-UX is now supported.

       ·   Amdahl UTS is now supported.

       ·   z/OS (formerly known as OS/390, formerly known as MVS OE) has now
	   support for dynamic loading.	 This is not selected by default,
	   however, you must specify -Dusedl in the arguments of Configure.

   Generic Improvements
       ·   Configure no longer includes the DBM libraries (dbm, gdbm, db,
	   ndbm) when building the Perl binary.	 The only exception to this is
	   SunOS 4.x, which needs them.

       ·   Some new Configure symbols, useful for extension writers:

		   For struct cmsghdr.

		   Whether fcntl() can be used for file locking.

		   For getpagesize(), though you should prefer

		   For struct msghdr.

		   Whether one needs to use Perl_va_copy() to copy varargs.

		   The number of elements in an array needed to hold all the
		   available signals.

		   Whether one needs to access character data aligned by U32
		   sized pointers.

       ·   Removed Configure symbols: the PDP-11 memory model settings: huge,
	   large, medium, models.

       ·   SOCKS support is now much more robust.

       ·   If your file system supports symbolic links you can build Perl
	   outside of the source directory by

		   mkdir perl/build/directory
		   cd perl/build/directory
		   sh /path/to/perl/source/Configure -Dmksymlinks ...

	   This will create in perl/build/directory a tree of symbolic links
	   pointing to files in /path/to/perl/source.  The original files are
	   left unaffected.  After Configure has finished you can just say

		   make all test

	   and Perl will be built and tested, all in perl/build/directory.

Selected Bug Fixes
       Numerous memory leaks and uninitialized memory accesses have been
       hunted down.  Most importantly anonymous subs used to leak quite a bit.

       ·   chop(@list) in list context returned the characters chopped in
	   reverse order.  This has been reversed to be in the right order.

       ·   The order of DESTROYs has been made more predictable.

       ·   mkdir() now ignores trailing slashes in the directory name, as
	   mandated by POSIX.

       ·   Attributes (like :shared) didn't work with our().

       ·   The PERL5OPT environment variable (for passing command line
	   arguments to Perl) didn't work for more than a single group of

       ·   The tainting behaviour of sprintf() has been rationalized.  It does
	   not taint the result of floating point formats anymore, making the
	   behaviour consistent with that of string interpolation.

       ·   All but the first argument of the IO syswrite() method are now

       ·   Tie::ARRAY SPLICE method was broken.

       ·   vec() now tries to work with characters <= 255 when possible, but
	   it leaves higher character values in place.	In that case, if vec()
	   was used to modify the string, it is no longer considered to be

   Platform Specific Changes and Fixes
       ·   Linux previously had problems related to sockaddrlen when using
	   accept(), revcfrom() (in Perl: recv()), getpeername(), and

       ·   Previously DYNIX/ptx had problems in its Configure probe for non-
	   blocking I/O.

       ·   Windows

	   ·	   Borland C++ v5.5 is now a supported compiler that can build
		   Perl.  However, the generated binaries continue to be
		   incompatible with those generated by the other supported
		   compilers (GCC and Visual C++).

	   ·	   Win32::GetCwd() correctly returns C:\ instead of C: when at
		   the drive root.  Other bugs in chdir() and Cwd::cwd() have
		   also been fixed.

	   ·	   Duping socket handles with open(F, ">&MYSOCK") now works
		   under Windows 9x.

	   ·	   HTML files will be installed in c:\perl\html instead of

	   ·	   The makefiles now provide a single switch to bulk-enable
		   all the features enabled in ActiveState ActivePerl (a
		   popular binary distribution).

New or Changed Diagnostics
       Two new debugging options have been added: if you have compiled your
       Perl with debugging, you can use the -DT and -DR options to trace
       tokenising and to add reference counts to displaying variables,

       ·   If an attempt to use a (non-blessed) reference as an array index is
	   made, a warning is given.

       ·   "push @a;" and "unshift @a;" (with no values to push or unshift)
	   now give a warning.	This may be a problem for generated and
	   eval'ed code.

Changed Internals
       ·   Some new APIs: ptr_table_clear(), ptr_table_free(), sv_setref_uv().
	   For the full list of the available APIs see perlapi.

       ·   dTHR and djSP have been obsoleted; the former removed (because it's
	   a no-op) and the latter replaced with dSP.

       ·   Perl now uses system malloc instead of Perl malloc on all 64-bit
	   platforms, and even in some not-always-64-bit platforms like AIX,
	   IRIX, and Solaris.  This change breaks backward compatibility but
	   Perl's malloc has problems with large address spaces and also the
	   speed of vendors' malloc is generally better in large address space
	   machines (Perl's malloc is mostly tuned for space).

New Tests
       Many new tests have been added.	The most notable is probably the
       lib/1_compile: it is very notable because running it takes quite a long
       time. It test compiles all the Perl modules in the distribution.
       Please be patient.

Known Problems
       Note that unlike other sections in this document (which describe
       changes since 5.7.0) this section is cumulative containing known
       problems for all the 5.7 releases.

   AIX vac May Produce Buggy Code For Perl
       The AIX C compiler vac version may produce buggy code,
       resulting in few random tests failing, but when the failing tests are
       run by hand, they succeed.  We suggest upgrading to at least vac
       version, that has been known to compile Perl correctly.	"lslpp
       -L|grep vac.C" will tell you the vac version.

   lib/ftmp-security tests warn 'system possibly insecure'
       Don't panic.  Read INSTALL 'make test' section instead.

   lib/io_multihomed Fails In LP64-Configured HP-UX
       The lib/io_multihomed test may hang in HP-UX if Perl has been
       configured to be 64-bit. Because other 64-bit platforms do not hang in
       this test, HP-UX is suspect. All other tests pass in 64-bit HP-UX. The
       test attempts to create and connect to "multihomed" sockets (sockets
       which have multiple IP addresses).

   Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
       If perl is configured with -Duse64bitall, the successful result of the
       subtest 10 of lib/posix may arrive before the successful result of the
       subtest 9, which confuses the test harness so much that it thinks the
       subtest 9 failed.

   lib/b test 19
       The test fails on various platforms (PA64 and IA64 are known), but the
       exact cause is still being investigated.

   Linux With Sfio Fails op/misc Test 48
       No known fix.

   sigaction test 13 in VMS
       The test is known to fail; whether it's because of VMS of because of
       faulty test is not known.

   sprintf tests 129 and 130
       The op/sprintf tests 129 and 130 are known to fail on some platforms.
       Examples include any platform using sfio, and Compaq/Tandem's NonStop-
       UX.  The failing platforms do not comply with the ANSI C Standard, line
       19ff on page 134 of ANSI X3.159 1989 to be exact.  (They produce
       something else than "1" and "-1" when formatting 0.6 and -0.6 using the
       printf format "%.0f", most often they produce "0" and "-0".)

   Failure of Thread tests
       The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
       fundamental problems in the 5.005 threading implementation. These are
       not new failures--Perl 5.005_0x has the same bugs, but didn't have
       these tests. (Note that support for 5.005-style threading remains

   Localising a Tied Variable Leaks Memory
	   use Tie::Hash;
	   tie my %tie_hash => 'Tie::StdHash';


	   local($tie_hash{Foo}) = 1; # leaks

       Code like the above is known to leak memory every time the local() is

   Self-tying of Arrays and Hashes Is Forbidden
       Self-tying of arrays and hashes is broken in rather deep and hard-to-
       fix ways.  As a stop-gap measure to avoid people from getting
       frustrated at the mysterious results (core dumps, most often) it is for
       now forbidden (you will get a fatal error even from an attempt).

   Building Extensions Can Fail Because Of Largefiles
       Some extensions like mod_perl are known to have issues with
       `largefiles', a change brought by Perl 5.6.0 in which file offsets
       default to 64 bits wide, where supported.  Modules may fail to compile
       at all or compile and work incorrectly.	Currently there is no good
       solution for the problem, but Configure now provides appropriate non-
       largefile ccflags, ldflags, libswanted, and libs in the %Config hash
       (e.g., $Config{ccflags_nolargefiles}) so the extensions that are having
       problems can try configuring themselves without the largefileness.
       This is admittedly not a clean solution, and the solution may not even
       work at all.  One potential failure is whether one can (or, if one can,
       whether it's a good idea) link together at all binaries with different
       ideas about file offsets, all this is platform-dependent.

   The Compiler Suite Is Still Experimental
       The compiler suite is slowly getting better but is nowhere near working
       order yet.

Reporting Bugs
       If you find what you think is a bug, you might check the articles
       recently posted to the comp.lang.perl.misc newsgroup and the perl bug
       database at  There may also be information at , the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug
       program included with your release.  Be sure to trim your bug down to a
       tiny but sufficient test case.  Your bug report, along with the output
       of "perl -V", will be sent off to to be analysed by
       the Perl porting team.

       The Changes file for exhaustive details on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.

       Written by Jarkko Hietaniemi <>, with many contributions from
       The Perl Porters and Perl Users submitting feedback and patches.

       Send omissions or corrections to <>.

perl v5.12.2			  2010-09-05		       PERL571DELTA(1)
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