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PERL570DELTA(1)	       Perl Programmers Reference Guide	       PERL570DELTA(1)

       perl570delta - what's new for perl v5.7.0

       This document describes differences between the 5.6.0 release and the
       5.7.0 release.

Security Vulnerability Closed
       A potential security vulnerability in the optional suidperl component
       of Perl has been identified.  suidperl is neither built nor installed
       by default.  As of September the 2nd, 2000, the only known vulnerable
       platform is Linux, most likely all Linux distributions.	CERT and
       various vendors have been alerted about the vulnerability.

       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
       the Perl 5.7.0 release, 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
       ·   Arrays now always interpolate into double-quoted strings:
	   constructs like "foo@bar" now always assume @bar is an array,
	   whether or not the compiler has seen use of @bar.

       ·   The semantics of bless(REF, REF) were unclear and until someone
	   proves it to make some sense, it is forbidden.

       ·   A reference to a reference now stringify as "REF(0x81485ec)"
	   instead of "SCALAR(0x81485ec)" in order to be more consistent with
	   the return value of ref().

       ·   The very dusty examples in the eg/ directory have been removed.
	   Suggestions for new shiny examples welcome but the main issue is
	   that the examples need to be documented, tested and (most
	   importantly) maintained.

       ·   The obsolete chat2 library that should never have been allowed to
	   escape the laboratory has been decommissioned.

       ·   The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are
	   still recognised but now cause fatal errors.	 The previous
	   behaviour of ignoring them by default and warning if requested was
	   unacceptable since it, in a way, falsely promised that the features
	   could be used.

       ·   The (bogus) escape sequences \8 and \9 now give an optional warning
	   ("Unrecognized escape passed through").  There is no need to
	   \-escape any "\w" character.

       ·   lstat(FILEHANDLE) now gives a warning because the operation makes
	   no sense.  In future releases this may become a fatal error.

       ·   The long deprecated uppercase aliases for the string comparison
	   operators (EQ, NE, LT, LE, GE, GT) have now been removed.

       ·   The regular expression captured submatches ($1, $2, ...) are now
	   more consistently unset if the match fails, instead of leaving
	   false data lying around in them.

       ·   The tr///C and tr///U features have been removed and will not
	   return; the interface was a mistake.	 Sorry about that.  For
	   similar functionality, see pack('U0', ...) and pack('C0', ...).

Core Enhancements
       ·   "perl -d:Module=arg,arg,arg" now works (previously one couldn't
	   pass in multiple arguments.)

       ·   my __PACKAGE__ $obj now works.

       ·   "no Module;" now works even if there is no "sub unimport" in the

       ·   The numerical comparison operators return "undef" if either operand
	   is a NaN.  Previously the behaviour was unspecified.

       ·   "pack('U0a*', ...)" can now be used to force a string to UTF-8.

       ·   prototype(\&) is now available.

       ·   There is now an UNTIE method.

Modules and Pragmata
   New Modules
       ·   File::Temp allows one to create temporary files and directories in
	   an easy, portable, and secure way.

       ·   Storable gives persistence to Perl data structures by allowing the
	   storage and retrieval of Perl data to and from files in a fast and
	   compact binary format.

   Updated And Improved Modules and Pragmata
       ·   The following independently supported modules have been updated to
	   newer versions from CPAN: CGI, CPAN, DB_File, File::Spec,
	   Getopt::Long, the podlators bundle, Pod::LaTeX, Pod::Parser,
	   Term::ANSIColor, Test.

       ·   Bug fixes and minor enhancements have been applied to B::Deparse,
	   Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
	   Math::Complex, Math::Trig, Net::protoent, the re pragma,
	   SelfLoader, Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and
	   the warnings pragma.

       ·   The attributes::reftype() now works on tied arguments.

       ·   AutoLoader can now be disabled with "no AutoLoader;",

       ·   The English module can now be used without the infamous performance
	   hit by saying

		   use English '-no_performance_hit';

	   (Assuming, of course, that one doesn't need the troublesome
	   variables "$`", $&, or "$'".)  Also, introduced @LAST_MATCH_START
	   and @LAST_MATCH_END English aliases for "@-" and "@+".

       ·   File::Find now has pre- and post-processing callbacks.  It also
	   correctly changes directories when chasing symbolic links.
	   Callbacks (naughtily) exiting with "next;" instead of "return;" now

       ·   File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
	   prototype mismatch with CORE::glob().

       ·   IPC::Open3 now allows the use of numeric file descriptors.

       ·   use lib now works identically to @INC.  Removing directories with
	   'no lib' now works.

       ·   %INC now localised in a Safe compartment so that use/require work.

       ·   The Shell module now has an OO interface.

Utility Changes
       ·   The Emacs perl mode (emacs/cperl-mode.el) has been updated to
	   version 4.31.

       ·   Perlbug is now much more robust.  It also sends the bug report to, not

       ·   The perlcc utility has been rewritten and its user interface (that
	   is, command line) is much more like that of the UNIX C compiler,

       ·   The xsubpp utility for extension writers now understands POD
	   documentation embedded in the *.xs files.

New Documentation
       ·   perl56delta details the changes between the 5.005 release and the
	   5.6.0 release.

       ·   perldebtut is a Perl debugging tutorial.

       ·   perlebcdic contains considerations for running Perl on EBCDIC
	   platforms.  Note that unfortunately EBCDIC platforms that used to
	   supported back in Perl 5.005 are still unsupported by Perl 5.7.0;
	   the plan, however, is to bring them back to the fold.

       ·   perlnewmod tells about writing and submitting a new module.

       ·   perlposix-bc explains using Perl on the POSIX-BC platform (an
	   EBCDIC mainframe platform).

       ·   perlretut is a regular expression tutorial.

       ·   perlrequick is a regular expressions quick-start guide.  Yes, much
	   quicker than perlretut.

       ·   perlutil explains the command line utilities packaged with the Perl

Performance Enhancements
       ·   map() that changes the size of the list should now work faster.

       ·   sort() has been changed to use mergesort internally as opposed to
	   the earlier quicksort.  For very small lists this may result in
	   slightly slower sorting times, but in general the speedup should be
	   at least 20%.  Additional bonuses are that the worst case behaviour
	   of sort() is now better (in computer science terms it now runs in
	   time O(N log N), as opposed to quicksort's Theta(N**2) worst-case
	   run time behaviour), and that sort() is now stable (meaning that
	   elements with identical keys will stay ordered as they were before
	   the sort).

Installation and Configuration Improvements
   Generic Improvements
       ·   INSTALL now explains how you can configure Perl to use 64-bit
	   integers even on non-64-bit platforms.

       · policy change: if you are reusing a file (see
	   INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
	   Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
	   them will now be changed to the new prefix, /foo/bar.  (Previously
	   only $prefix changed.)  If you do not like this new behaviour,
	   specify prefix, siteprefix, and vendorprefix explicitly.

       ·   A new optional location for Perl libraries, otherlibdirs, is
	   available.  It can be used for example for vendor add-ons without
	   disturbing Perl's own library directories.

       ·   In many platforms the vendor-supplied 'cc' is too stripped-down to
	   build Perl (basically, 'cc' doesn't do ANSI C).  If this seems to
	   be the case and 'cc' does not seem to be the GNU C compiler 'gcc',
	   an automatic attempt is made to find and use 'gcc' instead.

       ·   gcc needs to closely track the operating system release to avoid
	   build problems. If Configure finds that gcc was built for a
	   different operating system release than is running, it now gives a
	   clearly visible warning that there may be trouble ahead.

       ·   If binary compatibility with the 5.005 release is not wanted,
	   Configure no longer suggests including the 5.005 modules in @INC.

       ·   Configure "-S" can now run non-interactively.

       ·   configure.gnu now works with options with whitespace in them.

       ·   installperl now outputs everything to STDERR.

       ·   $Config{byteorder} is now computed dynamically (this is more robust
	   with "fat binaries" where an executable image contains binaries for
	   more than one binary platform.)

Selected Bug Fixes
       ·   Several debugger fixes: exit code now reflects the script exit
	   code, condition "0" now treated correctly, the "d" command now
	   checks line number, the $. no longer gets corrupted, all debugger
	   output now goes correctly to the socket if RemotePort is set.

       ·   *foo{FORMAT} now works.

       ·   Lexical warnings now propagating correctly between scopes.

       ·   Line renumbering with eval and "#line" now works.

       ·   Fixed numerous memory leaks, especially in eval "".

       ·   Modulus of unsigned numbers now works (4063328477 % 65535 used to
	   return 27406, instead of 27047).

       ·   Some "not a number" warnings introduced in 5.6.0 eliminated to be
	   more compatible with 5.005.	Infinity is now recognised as a

       ·   our() variables will not cause "will not stay shared" warnings.

       ·   pack "Z" now correctly terminates the string with "\0".

       ·   Fix password routines which in some shadow password platforms (e.g.
	   HP-UX) caused getpwent() to return every other entry.

       ·   printf() no longer resets the numeric locale to "C".

       ·   "q(a\\b)" now parses correctly as 'a\\b'.

       ·   Printing quads (64-bit integers) with printf/sprintf now works
	   without the q L ll prefixes (assuming you are on a quad-capable

       ·   Regular expressions on references and overloaded scalars now work.

       ·   scalar() now forces scalar context even when used in void context.

       ·   sort() arguments are now compiled in the right wantarray context
	   (they were accidentally using the context of the sort() itself).

       ·   Changed the POSIX character class "[[:space:]]" to include the
	   (very rare) vertical tab character.	Added a new POSIX-ish
	   character class "[[:blank:]]" which stands for horizontal
	   whitespace (currently, the space and the tab).

       ·   $AUTOLOAD, sort(), lock(), and spawning subprocesses in multiple
	   threads simultaneously are now thread-safe.

       ·   Allow read-only string on left hand side of non-modifying tr///.

       ·   Several Unicode fixes (but still not perfect).

	   ·	   BOMs (byte order marks) in the beginning of Perl files
		   (scripts, modules) should now be transparently skipped.
		   UTF-16 (UCS-2) encoded Perl files should now be read

	   ·	   The character tables have been updated to Unicode 3.0.1.

	   ·	   chr() for values greater than 127 now create utf8 when
		   under use utf8.

	   ·	   Comparing with utf8 data does not magically upgrade
		   non-utf8 data into utf8.

	   ·	   "IsAlnum", "IsAlpha", and "IsWord" now match titlecase.

	   ·	   Concatenation with the "." operator or via variable
		   interpolation, "eq", "substr", "reverse", "quotemeta", the
		   "x" operator, substitution with "s///", single-quoted
		   UTF-8, should now work--in theory.

	   ·	   The "tr///" operator now works slightly better but is still
		   rather broken.  Note that the "tr///CU" functionality has
		   been removed (but see pack('U0', ...)).

	   ·	   vec() now refuses to deal with characters >255.

	   ·	   Zero entries were missing from the Unicode classes like

       ·   UNIVERSAL::isa no longer caches methods incorrectly.	 (This broke
	   the Tk extension with 5.6.0.)

   Platform Specific Changes and Fixes
       ·   BSDI 4.*

	   Perl now works on post-4.0 BSD/OSes.

       ·   All BSDs

	   Setting $0 now works (as much as possible; see perlvar for

       ·   Cygwin

	   Numerous updates; currently synchronised with Cygwin 1.1.4.

       ·   EPOC

	   EPOC update after Perl 5.6.0.  See README.epoc.

       ·   FreeBSD 3.*

	   Perl now works on post-3.0 FreeBSDs.

       ·   HP-UX

	   README.hpux updated; "Configure -Duse64bitall" now almost works.

       ·   IRIX

	   Numerous compilation flag and hint enhancements; accidental mixing
	   of 32-bit and 64-bit libraries (a doomed attempt) made much harder.

       ·   Linux

	   Long doubles should now work (see INSTALL).

       ·   Mac OS Classic

	   Compilation of the standard Perl distribution in Mac OS Classic
	   should now work if you have the Metrowerks development environment
	   and the missing Mac-specific toolkit bits.  Contact the macperl
	   mailing list for details.

       ·   MPE/iX

	   MPE/iX update after Perl 5.6.0.  See README.mpeix.

       ·   NetBSD/sparc

	   Perl now works on NetBSD/sparc.

       ·   OS/2

	   Now works with usethreads (see INSTALL).

       ·   Solaris

	   64-bitness using the Sun Workshop compiler now works.

       ·   Tru64 (aka Digital UNIX, aka DEC OSF/1)

	   The operating system version letter now recorded in
	   $Config{osvers}.  Allow compiling with gcc (previously explicitly
	   forbidden).	Compiling with gcc still not recommended because buggy
	   code results, even with gcc 2.95.2.

       ·   Unicos

	   Fixed various alignment problems that lead into core dumps either
	   during build or later; no longer dies on math errors at runtime;
	   now using full quad integers (64 bits), previously was using only
	   46 bit integers for speed.

       ·   VMS

	   chdir() now works better despite a CRT bug; now works with
	   MULTIPLICITY (see INSTALL); now works with Perl's malloc.

       ·   Windows

	   ·	   accept() no longer leaks memory.

	   ·	   Better chdir() return value for a non-existent directory.

	   ·	   New %ENV entries now propagate to subprocesses.

	   ·	   $ENV{LIB} now used to search for libs under Visual C.

	   ·	   A failed (pseudo)fork now returns undef and sets errno to

	   ·	   Allow REG_EXPAND_SZ keys in the registry.

	   ·	   Can now send() from all threads, not just the first one.

	   ·	   Fake signal handling reenabled, bugs and all.

	   ·	   Less stack reserved per thread so that more threads can run
		   concurrently. (Still 16M per thread.)

	   ·	   "File::Spec->tmpdir()" now prefers C:/temp over /tmp (works
		   better when perl is running as service).

	   ·	   Better UNC path handling under ithreads.

	   ·	   wait() and waitpid() now work much better.

	   ·	   winsock handle leak fixed.

New or Changed Diagnostics
       All regular expression compilation error messages are now hopefully
       easier to understand both because the error message now comes before
       the failed regex and because the point of failure is now clearly

       The various "opened only for", "on closed", "never opened" warnings
       drop the "main::" prefix for filehandles in the "main" package, for
       example "STDIN" instead of <main::STDIN>.

       The "Unrecognized escape" warning has been extended to include "\8",
       "\9", and "\_".	There is no need to escape any of the "\w" characters.

Changed Internals
       ·   perlapi.pod (a companion to perlguts) now attempts to document the
	   internal API.

       ·   You can now build a really minimal perl called microperl.  Building
	   microperl does not require even running Configure; "make -f
	   Makefile.micro" should be enough.  Beware: microperl makes many
	   assumptions, some of which may be too bold; the resulting
	   executable may crash or otherwise misbehave in wondrous ways.  For
	   careful hackers only.

       ·   Added rsignal(), whichsig(), do_join() to the publicised API.

       ·   Made possible to propagate customised exceptions via croak()ing.

       ·   Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and

       ·   Now xsubs can have attributes just like subs.

Known Problems
   Unicode Support Still Far From Perfect
       We're working on it.  Stay tuned.

   EBCDIC Still A Lost Platform
       The plan is to bring them back.

   Building Extensions Can Fail Because Of Largefiles
       Certain extensions like mod_perl and BSD::Resource 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-

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

   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.

   Long Doubles Still Don't Work In Solaris
       The experimental long double support is still very much so in Solaris.
       (Other platforms like Linux and Tru64 are beginning to solidify in this

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

   Storable tests fail in some platforms
       If any Storable tests fail the use of Storable is not advisable.

       ·   Many Storable tests fail on AIX configured with 64 bit integers.

	   So far unidentified problems break Storable in AIX if Perl is
	   configured to use 64 bit integers.  AIX in 32-bit mode works and
	   other 64-bit platforms work with Storable.

       ·   DOS DJGPP may hang when testing Storable.

       ·   st-06compat fails in UNICOS and UNICOS/mk.

	   This means that you cannot read old (pre-Storable-0.7) Storable
	   images made in other platforms.

       ·   st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS
	   Alpha 7.2.

   Threads Are Still Experimental
       Multithreading is still an experimental feature.	 Some platforms emit
       the following message for lib/thr5005

	   # This is a KNOWN FAILURE, and one of the reasons why threading
	   # is still an experimental feature.	It is here to stop people
	   # from deploying threads in production. ;-)

       and another known thread-related warning is

	  pragma/overload......Unbalanced saves: 3 more saves than restores
	  panic: magic_mutexfree during global destruction.
	  lib/selfloader.......Unbalanced saves: 3 more saves than restores
	  panic: magic_mutexfree during global destruction.
	  lib/st-dclone........Unbalanced saves: 3 more saves than restores
	  panic: magic_mutexfree during global destruction.

   The Compiler Suite Is Still Experimental
       The compiler suite is slowly getting better but is nowhere near working
       order yet.  The backend part that has seen perhaps the most progress is
       the bytecode compiler.

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 v5.10.1			  2009-02-12		       PERL570DELTA(1)

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