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perl589delta - Man Page

what is new for perl v5.8.9


This document describes differences between the 5.8.8 release and the 5.8.9 release.


The 5.8.9 release will be the last significant release of the 5.8.x series. Any future releases of 5.8.x will likely only be to deal with security issues, and platform build failures. Hence you should look to migrating to 5.10.x, if you have not started already. See "Known Problems" for more information.

Incompatible Changes

A particular construction in the source code of extensions written in C++ may need changing. See "Changed Internals" for more details. All extensions written in C, most written in C++, and all existing compiled extensions are unaffected. This was necessary to improve C++ support.

Other than this, there are no changes intentionally incompatible with 5.8.8. If any exist, they are bugs and reports are welcome.

Core Enhancements

Unicode Character Database 5.1.0

The copy of the Unicode Character Database included in Perl 5.8 has been updated to 5.1.0 from 4.1.0. See <http://www.unicode.org/versions/Unicode5.1.0/#NotableChanges> for the notable changes.

stat and -X on directory handles

It is now possible to call stat and the -X filestat operators on directory handles. As both directory and file handles are barewords, there can be ambiguities over which was intended. In these situations the file handle semantics are preferred. Both also treat *FILE{IO} filehandles like *FILE filehandles.

Source filters in @INC

It's possible to enhance the mechanism of subroutine hooks in @INC by adding a source filter on top of the filehandle opened and returned by the hook. This feature was planned a long time ago, but wasn't quite working until now. See "require" in perlfunc for details. (Nicholas Clark)

Exceptions in constant folding

The constant folding routine is now wrapped in an exception handler, and if folding throws an exception (such as attempting to evaluate 0/0), perl now retains the current optree, rather than aborting the whole program. Without this change, programs would not compile if they had expressions that happened to generate exceptions, even though those expressions were in code that could never be reached at runtime. (Nicholas Clark, Dave Mitchell)


You can now use no followed by a version number to specify that you want to use a version of perl older than the specified one.

Improved internal UTF-8 caching code

The code that caches calculated UTF-8 byte offsets for character offsets for a string has been re-written. Several bugs have been located and eliminated, and the code now makes better use of the information it has, so should be faster. In particular, it doesn't scan to the end of a string before calculating an offset within the string, which should speed up some operations on long strings. It is now possible to disable the caching code at run time, to verify that it is not the cause of suspected problems.

Runtime relocatable installations

There is now Configure support for creating a perl tree that is relocatable at run time. see "Relocatable installations".

New internal variables


This variable gives the native status returned by the last pipe close, backtick command, successful call to wait or waitpid, or from the system operator. See perlvar for details. (Contributed by Gisle Aas.)


This variable controls the state of the internal UTF-8 offset caching code. 1 for on (the default), 0 for off, -1 to debug the caching code by checking all its results against linear scans, and panicking on any discrepancy.

readpipe is now overridable

The built-in function readpipe is now overridable. Overriding it permits also to override its operator counterpart, qx// (also known as ).

simple exception handling macros

Perl 5.8.9 (and 5.10.0 onwards) now provides a couple of macros to do very basic exception handling in XS modules. You can use these macros if you call code that may croak, but you need to do some cleanup before giving control back to Perl. See "Exception Handling" in perlguts for more details.

-D option enhancements

  • -Dq suppresses the EXECUTING... message when running under -D
  • -Dl logs runops loop entry and exit, and jump level popping.
  • -Dv displays the process id as part of the trace output.

XS-assisted SWASHGET

Some pure-perl code that the regexp engine was using to retrieve Unicode properties and transliteration mappings has been reimplemented in XS for faster execution. (SADAHIRO Tomoyuki)

Constant subroutines

The interpreter internals now support a far more memory efficient form of inlineable constants. Storing a reference to a constant value in a symbol table is equivalent to a full typeglob referencing a constant subroutine, but using about 400 bytes less memory. This proxy constant subroutine is automatically upgraded to a real typeglob with subroutine if necessary. The approach taken is analogous to the existing space optimisation for subroutine stub declarations, which are stored as plain scalars in place of the full typeglob.

However, to aid backwards compatibility of existing code, which (wrongly) does not expect anything other than typeglobs in symbol tables, nothing in core uses this feature, other than the regression tests.

Stubs for prototyped subroutines have been stored in symbol tables as plain strings, and stubs for unprototyped subroutines as the number -1, since 5.005, so code which assumes that the core only places typeglobs in symbol tables has been making incorrect assumptions for over 10 years.

New Platforms

Compile support added for:

Modules and Pragmata

New Modules

  • Module::Pluggable is a simple framework to create modules that accept pluggable sub-modules. The bundled version is 3.8
  • Module::CoreList is a hash of hashes that is keyed on perl version as indicated in $]. The bundled version is 2.17
  • Win32API::File now available in core on Microsoft Windows. The bundled version is 0.1001_01
  • Devel::InnerPackage finds all the packages defined by a single file. It is part of the Module::Pluggable distribution. The bundled version is 0.3

Updated Modules

  • attributes upgraded to version 0.09
  • AutoLoader upgraded to version 5.67
  • AutoSplit upgraded to 1.06
  • autouse upgraded to version 1.06
  • B upgraded from 1.09_01 to 1.19

    • provides new pad related abstraction macros B::NV::COP_SEQ_RANGE_LOW, B::NV::COP_SEQ_RANGE_HIGH, B::NV::PARENT_PAD_INDEX, B::NV::PARENT_FAKELEX_FLAGS, which hides the difference in storage in 5.10.0 and later.
    • provides B::sub_generation, which exposes PL_sub_generation
    • provides B::GV::isGV_with_GP, which on pre-5.10 perls always returns true.
    • New type B::HE added with methods VAL, HASH and SVKEY_force
    • The B::GVf_IMPORTED_CV flag is now set correctly when a proxy constant subroutine is imported.
    • bugs fixed in the handling of PMOPs.
    • B::BM::PREVIOUS returns now U32, not U16. B::CV::START and B:CV::ROOT return now NULL on an XSUB, B::CV::XSUB and B::CV::XSUBANY return 0 on a non-XSUB.
  • B::C upgraded to 1.05
  • B::Concise upgraded to 0.76

    • new option -src causes the rendering of each statement (starting with the nextstate OP) to be preceded by the first line of source code that generates it.
    • new option -stash="somepackage", requires "somepackage", and then renders each function defined in its namespace.
    • now has documentation of detailed hint symbols.
  • B::Debug upgraded to version 1.05
  • B::Deparse upgraded to version 0.87

    • properly deparse print readpipe $x, $y.
    • now handles ”->(), ::(), sub :: {}, etc. correctly [RT #43010]. All bugs in parsing these kinds of syntax are now fixed:

          perl -MO=Deparse -e '"my %h = "->()'
          perl -MO=Deparse -e '::->()'
          perl -MO=Deparse -e 'sub :: {}'
          perl -MO=Deparse -e 'package a; sub a::b::c {}'
          perl -MO=Deparse -e 'sub the::main::road {}'
    • does not deparse $^H{v_string}, which is automatically set by the internals.
  • B::Lint upgraded to version 1.11
  • B::Terse upgraded to version 1.05
  • base upgraded to version 2.13

    • loading a module via base.pm would mask a global $SIG{__DIE__} in that module.
    • push all classes at once in @ISA
  • Benchmark upgraded to version 1.10
  • bigint upgraded to 0.23
  • bignum upgraded to 0.23
  • bigrat upgraded to 0.23
  • blib upgraded to 0.04
  • Carp upgraded to version 1.10

    The argument backtrace code now shows undef as undef, instead of a string "undef".

  • CGI upgraded to version 3.42
  • charnames upgraded to 1.06
  • constant upgraded to version 1.17
  • CPAN upgraded to version 1.9301
  • Cwd upgraded to version 3.29 with some platform specific improvements (including for VMS).
  • Data::Dumper upgraded to version 2.121_17

    • Fixes hash iterator current position with the pure Perl version [RT #40668]
    • Performance enhancements, which will be most evident on platforms where repeated calls to C's realloc() are slow, such as Win32.
  • DB_File upgraded to version 1.817
  • DB_Filter upgraded to version 0.02
  • Devel::DProf upgraded to version 20080331.00
  • Devel::Peek upgraded to version 1.04
  • Devel::PPPort upgraded to version 3.14
  • diagnostics upgraded to version 1.16
  • Digest upgraded to version 1.15
  • Digest::MD5 upgraded to version 2.37
  • DirHandle upgraded to version 1.02

    • now localises $., $@, $!, $^E, and $? before closing the directory handle to suppress leaking any side effects of warnings about it already being closed.
  • DynaLoader upgraded to version 1.09

    DynaLoader can now dynamically load a loadable object from a file with a non-default file extension.

  • Encode upgraded to version 2.26

    Encode::Alias includes a fix for encoding "646" on Solaris (better known as ASCII).

  • English upgraded to version 1.03
  • Errno upgraded to version 1.10
  • Exporter upgraded to version 5.63
  • ExtUtils::Command upgraded to version 1.15
  • ExtUtils::Constant upgraded to version 0.21
  • ExtUtils::Embed upgraded to version 1.28
  • ExtUtils::Install upgraded to version 1.50_01
  • ExtUtils::Installed upgraded to version 1.43
  • ExtUtils::MakeMaker upgraded to version 6.48

    • support for INSTALLSITESCRIPT and INSTALLVENDORSCRIPT configuration.
  • ExtUtils::Manifest upgraded to version 1.55
  • ExtUtils::ParseXS upgraded to version 2.19
  • Fatal upgraded to version 1.06

    • allows built-ins in CORE::GLOBAL to be made fatal.
  • Fcntl upgraded to version 1.06
  • fields upgraded to version 2.12
  • File::Basename upgraded to version 2.77
  • FileCache upgraded to version 1.07
  • File::Compare upgraded to 1.1005
  • File::Copy upgraded to 2.13

    • now uses 3-arg open.
  • File::DosGlob upgraded to 1.01
  • File::Find upgraded to version 1.13
  • File::Glob upgraded to version 1.06

    • fixes spurious results with brackets inside braces.
  • File::Path upgraded to version 2.07_02
  • File::Spec upgraded to version 3.29

    • improved handling of bad arguments.
    • some platform specific improvements (including for VMS and Cygwin), with an optimisation on abs2rel when handling both relative arguments.
  • File::stat upgraded to version 1.01
  • File::Temp upgraded to version 0.20
  • filetest upgraded to version 1.02
  • Filter::Util::Call upgraded to version 1.07
  • Filter::Simple upgraded to version 0.83
  • FindBin upgraded to version 1.49
  • GDBM_File upgraded to version 1.09
  • Getopt::Long upgraded to version 2.37
  • Getopt::Std upgraded to version 1.06
  • Hash::Util upgraded to version 0.06
  • if upgraded to version 0.05
  • IO upgraded to version 1.23

    Reduced number of calls to getpeername in IO::Socket

  • IPC::Open upgraded to version 1.03
  • IPC::Open3 upgraded to version 1.03
  • IPC::SysV upgraded to version 2.00
  • lib upgraded to version 0.61

    • avoid warning about loading .par files.
  • libnet upgraded to version 1.22
  • List::Util upgraded to 1.19
  • Locale::Maketext upgraded to 1.13
  • Math::BigFloat upgraded to version 1.60
  • Math::BigInt upgraded to version 1.89
  • Math::BigRat upgraded to version 0.22

    • implements new as_float method.
  • Math::Complex upgraded to version 1.54.
  • Math::Trig upgraded to version 1.18.
  • NDBM_File upgraded to version 1.07

    • improve g++ handling for systems using GDBM compatibility headers.
  • Net::Ping upgraded to version 2.35
  • NEXT upgraded to version 0.61

    • fix several bugs with NEXT when working with AUTOLOAD, eval block, and within overloaded stringification.
  • ODBM_File upgraded to 1.07
  • open upgraded to 1.06
  • ops upgraded to 1.02
  • PerlIO::encoding upgraded to version 0.11
  • PerlIO::scalar upgraded to version 0.06

    • [RT #40267] PerlIO::scalar doesn't respect readonly-ness.
  • PerlIO::via upgraded to version 0.05
  • Pod::Html upgraded to version 1.09
  • Pod::Parser upgraded to version 1.35
  • Pod::Usage upgraded to version 1.35
  • POSIX upgraded to version 1.15

    • POSIX constants that duplicate those in Fcntl are now imported from Fcntl and re-exported, rather than being duplicated by POSIX
    • POSIX::remove can remove empty directories.
    • POSIX::setlocale safer to call multiple times.
    • POSIX::SigRt added, which provides access to POSIX realtime signal functionality on systems that support it.
  • re upgraded to version 0.06_01
  • Safe upgraded to version 2.16
  • Scalar::Util upgraded to 1.19
  • SDBM_File upgraded to version 1.06
  • SelfLoader upgraded to version 1.17
  • Shell upgraded to version 0.72
  • sigtrap upgraded to version 1.04
  • Socket upgraded to version 1.81

    • this fixes an optimistic use of gethostbyname
  • Storable upgraded to 2.19
  • Switch upgraded to version 2.13
  • Sys::Syslog upgraded to version 0.27
  • Term::ANSIColor upgraded to version 1.12
  • Term::Cap upgraded to version 1.12
  • Term::ReadLine upgraded to version 1.03
  • Test::Builder upgraded to version 0.80
  • Test::Harness upgraded version to 2.64

    • this makes it able to handle newlines.
  • Test::More upgraded to version 0.80
  • Test::Simple upgraded to version 0.80
  • Text::Balanced upgraded to version 1.98
  • Text::ParseWords upgraded to version 3.27
  • Text::Soundex upgraded to version 3.03
  • Text::Tabs upgraded to version 2007.1117
  • Text::Wrap upgraded to version 2006.1117
  • Thread upgraded to version 2.01
  • Thread::Semaphore upgraded to version 2.09
  • Thread::Queue upgraded to version 2.11

    • added capability to add complex structures (e.g., hash of hashes) to queues.
    • added capability to dequeue multiple items at once.
    • added new methods to inspect and manipulate queues:  peek, insert and extract
  • Tie::Handle upgraded to version 4.2
  • Tie::Hash upgraded to version 1.03
  • Tie::Memoize upgraded to version 1.1

    • Tie::Memoize::EXISTS now correctly caches its results.
  • Tie::RefHash upgraded to version 1.38
  • Tie::Scalar upgraded to version 1.01
  • Tie::StdHandle upgraded to version 4.2
  • Time::gmtime upgraded to version 1.03
  • Time::Local upgraded to version 1.1901
  • Time::HiRes upgraded to version 1.9715 with various build improvements  (including VMS) and minor platform-specific bug fixes (including for HP-UX 11 ia64).
  • threads upgraded to 1.71

    • new thread state information methods: is_running, is_detached and is_joinable.  list method enhanced to return running or joinable threads.
    • new thread signal method: kill
    • added capability to specify thread stack size.
    • added capability to control thread exiting behavior.  Added a new exit method.
  • threads::shared upgraded to version 1.27

    • smaller and faster implementation that eliminates one internal structure and the consequent level of indirection.
    • user locks are now stored in a safer manner.
    • new function shared_clone creates a copy of an object leaving shared elements as-is and deep-cloning non-shared elements.
    • added new is_shared method.
  • Unicode::Normalize upgraded to version 1.02
  • Unicode::UCD upgraded to version 0.25
  • warnings upgraded to version 1.05_01
  • Win32 upgraded to version 0.38

    • added new function GetCurrentProcessId which returns the regular Windows process identifier of the current process, even when called from within a fork.
  • XSLoader upgraded to version 0.10
  • XS::APItest and XS::Typemap are for internal use only and hence no longer installed. Many more tests have been added to XS::APItest.

Utility Changes

debugger upgraded to version 1.31

  • Andreas König contributed two functions to save and load the debugger history.
  • NEXT::AUTOLOAD no longer emits warnings under the debugger.
  • The debugger should now correctly find tty the device on OS X 10.5 and VMS when the program forks.
  • LVALUE subs now work inside the debugger.


Perl 5.8.9 adds a new utility perlthanks, which is a variant of perlbug, but for sending non-bug-reports to the authors and maintainers of Perl. Getting nothing but bug reports can become a bit demoralising - we'll see if this changes things.


perlbug now checks if you're reporting about a non-core module and suggests you report it to the CPAN author instead.


  • won't define an empty string as a constant [RT #25366]
  • has examples for h2xs -X


  • now attempts to deal sensibly with the difference in path implications between "" and <> quoting in #include statements.
  • now generates correct code for #if defined A || defined B [RT #39130]

New Documentation

As usual, the documentation received its share of corrections, clarifications and other nitfixes. More tags were added for indexing.

perlunitut is a tutorial written by Juerd Waalboer on Unicode-related terminology and how to correctly handle Unicode in Perl scripts.

perlunicode is updated in section user defined properties.

perluniintro has been updated in the example of detecting data that is not valid in particular encoding.

perlcommunity provides an overview of the Perl Community along with further resources.

CORE documents the pseudo-namespace for Perl's core routines.

Changes to Existing Documentation

perlglossary adds deprecated modules and features and to be dropped modules.

perlhack has been updated and added resources on smoke testing.

The Perl FAQs (perlfaq1..perlfaq9) have been updated.

perlcheat is updated with better details on \w, \d, and \s.

perldebug is updated with information on how to call the debugger.

perldiag documentation updated with subroutine with an ampersand on the argument to exists and delete and also several terminology updates on warnings.

perlfork documents the limitation of exec inside pseudo-processes.


perllocale documentation is adjusted for number localization and POSIX::setlocale to fix Debian bug #379463.

perlmodlib is updated with CPAN::API::HOWTO and Sys::Syslog::win32::Win32

perlre documentation updated to reflect the differences between [[:xxxxx:]] and \p{IsXxxxx} matches. Also added section on /g and /c modifiers.

perlreguts describe the internals of the regular expressions engine. It has been contributed by Yves Orton.

perlrebackslash describes all perl regular expression backslash and escape sequences.

perlrecharclass describes the syntax and use of character classes in Perl Regular Expressions.

perlrun is updated to clarify on the hash seed PERL_HASH_SEED. Also more information in options -x and -u.

perlsub example is updated to use a lexical variable for opendir syntax.

perlvar fixes confusion about real GID $( and effective GID $).

Perl thread tutorial example is fixed in section "Queues: Passing Data Around" in perlthrtut and perlthrtut.

perlhack documentation extensively improved by Jarkko Hietaniemi and others.

perltoot provides information on modifying @UNIVERSAL::ISA.

perlport documentation extended to include different kill(-9, ...) semantics on Windows. It also clearly states dump is not supported on Win32 and cygwin.

INSTALL has been updated and modernised.

Performance Enhancements

Installation and Configuration Improvements

Relocatable installations

There is now Configure support for creating a relocatable perl tree. If you Configure with -Duserelocatableinc, then the paths in @INC (and everything else in %Config) can be optionally located via the path of the perl executable.

At start time, if any paths in @INC or Config that Configure marked as relocatable (by starting them with ".../"), then they are prefixed the directory of $^X. This allows the relocation can be configured on a per-directory basis, although the default with -Duserelocatableinc is that everything is relocated. The initial install is done to the original configured prefix.

Configuration improvements

Configure is now better at removing temporary files. Tom Callaway (from RedHat) also contributed patches that complete the set of flags passed to the compiler and the linker, in particular that -fPIC is now enabled on Linux. It will also croak when your /dev/null isn't a device.

A new configuration variable d_pseudofork has been to Configure, and is available as  $Config{d_pseudofork} in the Config module. This distinguishes real fork support from the pseudofork emulation used on Windows platforms.

Config.pod and config.sh are now placed correctly for cross-compilation.

$Config{useshrplib} is now 'true' rather than 'yes' when using a shared perl library.

Compilation improvements

Parallel makes should work properly now, although there may still be problems if make test is instructed to run in parallel.

Many compilation warnings have been cleaned up. A very stubborn compiler warning in S_emulate_eaccess() was killed after six attempts. g++ support has been tuned, especially for FreeBSD.

mkppport has been integrated, and all ppport.h files in the core will now be autogenerated at build time (and removed during cleanup).

Installation improvements

installman now works with -Duserelocatableinc and DESTDIR.

installperl no longer installs:

  • static library files of statically linked extensions when a shared perl library is being used. (They are not needed. See "Windows" below).
  • SIGNATURE and PAUSE*.pub (CPAN files)
  • NOTES and PATCHING (ExtUtils files)
  • perlld and ld2 (Cygwin files)

Platform Specific Changes

There are improved hints for AIX, Cygwin, DEC/OSF, FreeBSD, HP/UX, Irix 6 Linux, MachTen, NetBSD, OS/390, QNX, SCO, Solaris, SunOS, System V Release 5.x (UnixWare 7, OpenUNIX 8), Ultrix, UMIPS, uts and VOS.


  • Drop -std=c89 and -ansi if using long long as the main integral type, else in FreeBSD 6.2 (and perhaps other releases), system headers do not declare some functions required by perl.


  • Starting with Solaris 10, we do not want versioned shared libraries, because those often indicate a private use only library. These problems could often be triggered when SUNWbdb (Berkeley DB) was installed. Hence if Solaris 10 is detected set ignore_versioned_solibs=y.


  • Allow IEEE math to be deselected on OpenVMS I64 (but it remains the default).
  • Record IEEE usage in config.h
  • Help older VMS compilers by using ccflags when building munchconfig.exe.
  • Don't try to build old Thread extension on VMS when -Duseithreads has been chosen.
  • Passing a raw string of "NaN" to nawk causes a core dump - so the string has been changed to "*NaN*"
  • t/op/stat.t tests will now test hard links on VMS if they are supported.


  • When using a shared perl library installperl no longer installs static library files, import library files and export library files (of statically linked extensions) and empty bootstrap files (of dynamically linked extensions). This fixes a problem building PAR-Packer on Win32 with a debug build of perl.
  • Various improvements to the win32 build process, including support for Visual C++ 2005 Express Edition (aka Visual C++ 8.x).
  • perl.exe will now have an icon if built with MinGW or Borland.
  • Improvements to the perl-static.exe build process.
  • Add Win32 makefile option to link all extensions statically.
  • The WinCE directory has been merged into the Win32 directory.
  • setlocale tests have been re-enabled for Windows XP onwards.

Selected Bug Fixes


Many many bugs related to the internal Unicode implementation (UTF-8) have been fixed. In particular, long standing bugs related to returning Unicode via tie, overloading or $@ are now gone, some of which were never reported.

unpack will internally convert the string back from UTF-8 on numeric types. This is a compromise between the full consistency now in 5.10, and the current behaviour, which is often used as a "feature" on string types.

Using :crlf and UTF-16 IO layers together will now work.

Fixed problems with split, Unicode /\s+/ and / \0/.

Fixed bug RT #40641 - encoding of Unicode characters in regular expressions.

Fixed a bug where using certain patterns in a regexp led to a panic. [RT #45337]

Perl no longer segfaults (due to infinite internal recursion) if the locale's character is not UTF-8 [RT #41442]:

    use open ':locale';
    print STDERR "\x{201e}"; # &bdquo;


Inconsistencies have been fixed in the reference counting PerlIO uses to keep track of Unix file descriptors, and the API used by XS code to manage getting and releasing FILE *s


Several bugs have been fixed in Magic, the internal system used to implement features such as tie, tainting and threads sharing.

undef @array on a tied array now correctly calls the CLEAR method.

Some of the bitwise ops were not checking whether their arguments were magical before using them. [RT #24816]

Magic is no longer invoked twice by the expression \&$x

A bug with assigning large numbers and tainting has been resolved. [RT #40708]

A new entry has been added to the MAGIC vtable - svt_local. This is used when copying magic to the new value during local, allowing certain problems with localising shared variables to be resolved.

For the implementation details, see "Magic Virtual Tables" in perlguts.

Reblessing overloaded objects now works

Internally, perl object-ness is on the referent, not the reference, even though methods can only be called via a reference. However, the original implementation of overloading stored flags related to overloading on the reference, relying on the flags being copied when the reference was copied, or set at the creation of a new reference. This manifests in a bug - if you rebless an object from a class that has overloading, into one that does not, then any other existing references think that they (still) point to an overloaded object, choose these C code paths, and then throw errors. Analogously, blessing into an overloaded class when other references exist will result in them not using overloading.

The implementation has been fixed for 5.10, but this fix changes the semantics of flag bits, so is not binary compatible, so can't be applied to 5.8.9. However, 5.8.9 has a work-around that implements the same bug fix. If the referent has multiple references, then all the other references are located and corrected. A full search is avoided whenever possible by scanning lexicals outwards from the current subroutine, and the argument stack.

A certain well known Linux vendor applied incomplete versions of this bug fix to their /usr/bin/perl and then prematurely closed bug reports about performance issues without consulting back upstream. This not being enough, they then proceeded to ignore the necessary fixes to these unreleased changes for 11 months, until massive pressure was applied by their long-suffering paying customers, catalysed by the failings being featured on a prominent blog and Slashdot.

strict now propagates correctly into string evals

Under 5.8.8 and earlier:

    $ perl5.8.8 -e 'use strict; eval "use foo bar" or die $@'
    Can't locate foo.pm in @INC (@INC contains: ... .) at (eval 1) line 2.
    BEGIN failed--compilation aborted at (eval 1) line 2.

Under 5.8.9 and later:

    $ perl5.8.9 -e 'use strict; eval "use foo bar" or die $@'
    Bareword "bar" not allowed while "strict subs" in use at (eval 1) line 1.

This may cause problems with programs that parse the error message and rely on the buggy behaviour.

Other fixes

  • The tokenizer no longer treats =cute (and other words beginning with =cut) as a synonym for =cut.
  • Calling CORE::require

    CORE::require and CORE::do were always parsed as require and do when they were overridden. This is now fixed.

  • Stopped memory leak on long /etc/groups entries.
  • while (my $x ...) { ...; redo } shouldn't undef $x.

    In the presence of my in the conditional of a while(), until(), or for(;;) loop, we now add an extra scope to the body so that redo doesn't undef the lexical.

  • The encoding pragma now correctly ignores anything following an @  character in the LC_ALL and LANG environment variables. [RT # 49646]
  • A segfault observed with some gcc 3.3 optimisations is resolved.
  • A possible segfault when unpack used in scalar context with () groups is resolved. [RT #50256]
  • Resolved issue where $! could be changed by a signal handler interrupting a system call.
  • Fixed bug RT #37886, symbolic dereferencing was allowed in the argument of defined even under the influence of use strict 'refs'.
  • Fixed bug RT #43207, where lc/uc inside sort affected the return value.
  • Fixed bug RT #45607, where *{"BONK"} = \&{"BONK"} didn't work correctly.
  • Fixed bug RT #35878, croaking from a XSUB called via goto &xsub corrupts perl internals.
  • Fixed bug RT #32539, DynaLoader.o is moved into libperl.so to avoid the need to statically link DynaLoader into the stub perl executable. With this libperl.so provides everything needed to get a functional embedded perl interpreter to run.
  • Fix bug RT #36267 so that assigning to a tied hash doesn't change the underlying hash.
  • Fix bug RT #6006, regexp replaces using large replacement variables fail some of the time, i.e. when substitution contains something like ${10} (note the bracket) instead of just $10.
  • Fix bug RT #45053, Perl_newCONSTSUB() is now thread safe.

Platform Specific Fixes

Darwin / MacOS X

  • Various improvements to 64 bit builds.
  • Mutex protection added in PerlIOStdio_close() to avoid race conditions. Hopefully this fixes failures in the threads tests free.t and blocks.t.
  • Added forked terminal support to the debugger, with the ability to update the window title.


  • A build problem with specifying USE_MULTI and USE_ITHREADS but without USE_IMP_SYS has been fixed.
  • OS2::REXX upgraded to version 1.04


  • Aligned floating point build policies for cc and gcc.

RedHat Linux

  • Revisited a patch from 5.6.1 for RH7.2 for Intel's icc [RT #7916], added an additional check for $Config{gccversion}.


  • Use -DPTR_IS_LONG when using 64 bit integers


  • Fixed PerlIO::Scalar in-memory file record-style reads.
  • pipe shutdown at process exit should now be more robust.
  • Bugs in VMS exit handling tickled by Test::Harness 2.64 have been fixed.
  • Fix fcntl() locking capability test in configure.com.
  • Replaced shrplib='define' with useshrplib='true' on VMS.


  • File::Find used to fail when the target directory is a bare drive letter and no_chdir is 1 (the default is 0). [RT #41555]
  • A build problem with specifying USE_MULTI and USE_ITHREADS but without USE_IMP_SYS has been fixed.
  • The process id is no longer truncated to 16 bits on some Windows platforms ( http://bugs.activestate.com/show_bug.cgi?id=72443 )
  • Fixed bug RT #54828 in perlio.c where calling binmode on Win32 and Cygwin may cause a segmentation fault.

Smaller fixes

  • It is now possible to overload eq when using nomethod.
  • Various problems using overload with 64 bit integers corrected.
  • The reference count of PerlIO file descriptors is now correctly handled.
  • On VMS, escaped dots will be preserved when converted to Unix syntax.
  • keys %+ no longer throws an 'ambiguous' warning.
  • Using #!perl -d could trigger an assertion, which has been fixed.
  • Don't stringify tied code references in @INC when calling require.
  • Code references in @INC report the correct file name when __FILE__ is used.
  • Width and precision in sprintf didn't handle characters above 255 correctly. [RT #40473]
  • List slices with indices out of range now work more consistently. [RT #39882]
  • A change introduced with perl 5.8.1 broke the parsing of arguments of the form -foo=bar with the -s on the <#!> line. This has been fixed. See http://bugs.activestate.com/show_bug.cgi?id=43483
  • tr/// is now threadsafe. Previously it was storing a swash inside its OP, rather than in a pad.
  • pod2html labels anchors more consistently and handles nested definition lists better.
  • threads cleanup veto has been extended to include perl_free() and perl_destruct()
  • On some systems, changes to $ENV{TZ} would not always be respected by the underlying calls to localtime_r().  Perl now forces the inspection of the environment on these systems.
  • The special variable $^R is now more consistently set when executing regexps using the (?{...}) construct.  In particular, it will still be set even if backreferences or optional sub-patterns (?:...)? are used.

New or Changed Diagnostics

panic: sv_chop %s

This new fatal error occurs when the C routine Perl_sv_chop() was passed a position that is not within the scalar's string buffer. This is caused by buggy XS code, and at this point recovery is not possible.

Maximal count of pending signals (%s) exceeded

This new fatal error occurs when the perl process has to abort due to too many pending signals, which is bound to prevent perl from being able to handle further incoming signals safely.

panic: attempt to call %s in %s

This new fatal error occurs when the ACL version file test operator is used where it is not available on the current platform. Earlier checks mean that it should never be possible to get this.

FETCHSIZE returned a negative value

New error indicating that a tied array has claimed to have a negative number of elements.

Can't upgrade %s (%d) to %d

Previously the internal error from the SV upgrade code was the less informative Can't upgrade that kind of scalar. It now reports the current internal type, and the new type requested.

%s argument is not a HASH or ARRAY element or a subroutine

This error, thrown if an invalid argument is provided to exists now correctly includes "or a subroutine". [RT #38955]

Cannot make the non-overridable builtin %s fatal

This error in Fatal previously did not show the name of the builtin in question (now represented by %s above).

Unrecognized character '%s' in column %d

This error previously did not state the column.

Offset outside string

This can now also be generated by a seek on a file handle using PerlIO::scalar.

Invalid escape in the specified encoding in regexp; marked by <-- HERE in m/%s/

New error, introduced as part of the fix to RT #40641 to handle encoding of Unicode characters in regular expression comments.

Your machine doesn't support dump/undump

A more informative fatal error issued when calling dump on Win32 and Cygwin. (Given that the purpose of dump is to abort with a core dump, and core dumps can't be produced on these platforms, this is more useful than silently exiting.)

Changed Internals

The perl sources can now be compiled with a C++ compiler instead of a C compiler. A necessary implementation details is that under C++, the macro XS used to define XSUBs now includes an extern "C" definition. A side effect of this is that C++ code that used the construction

    typedef XS(SwigPerlWrapper);

now needs to be written

    typedef XSPROTO(SwigPerlWrapper);

using the new XSPROTO macro, in order to compile. C extensions are unaffected, although C extensions are encouraged to use XSPROTO too. This change was present in the 5.10.0 release of perl, so any actively maintained code that happened to use this construction should already have been adapted. Code that needs changing will fail with a compilation error.

set magic on localizing/assigning to a magic variable will now only trigger for container magics, i.e. it will for %ENV or %SIG but not for $#array.

The new API macro newSVpvs() can be used in place of constructions such as newSVpvn("ISA", 3). It takes a single string constant, and at C compile time determines its length.

The new API function Perl_newSV_type() can be used as a more efficient replacement of the common idiom

    sv = newSV(0);
    sv_upgrade(sv, type);

Similarly Perl_newSVpvn_flags() can be used to combine Perl_newSVpv() with Perl_sv_2mortal() or the equivalent Perl_sv_newmortal() with Perl_sv_setpvn()

Two new macros mPUSHs() and mXPUSHs() are added, to make it easier to push mortal SVs onto the stack. They were then used to fix several bugs where values on the stack had not been mortalised.

A Perl_signbit() function was added to test the sign of an NV. It  maps to the system one when available.

Perl_av_reify(), Perl_lex_end(), Perl_mod(), Perl_op_clear(), Perl_pop_return(), Perl_qerror(), Perl_setdefout(), Perl_vivify_defelem() and Perl_yylex() are now visible to extensions. This was required to allow Data::Alias to work on Windows.

Perl_find_runcv() is now visible to perl core extensions. This was required to allow Sub::Current to work on Windows.

ptr_table* functions are now available in unthreaded perl. Storable takes advantage of this.

There have been many small cleanups made to the internals. In particular, Perl_sv_upgrade() has been simplified considerably, with a straight-through code path that uses memset() and memcpy() to initialise the new body, rather than assignment via multiple temporary variables. It has also benefited from simplification and de-duplication of the arena management code.

A lot of small improvements in the code base were made due to reports from the Coverity static code analyzer.

Corrected use and documentation of Perl_gv_stashpv(), Perl_gv_stashpvn(), Perl_gv_stashsv() functions (last parameter is a bitmask, not boolean).

PERL_SYS_INIT, PERL_SYS_INIT3 and PERL_SYS_TERM macros have been changed into functions.

PERLSYS_TERM no longer requires a context. PerlIO_teardown() is now called without a context, and debugging output in this function has been disabled because that required that an interpreter was present, an invalid assumption at termination time.

All compile time options which affect binary compatibility have been grouped together into a global variable (PL_bincompat_options).

The values of PERL_REVISION, PERL_VERSION and PERL_SUBVERSION are now baked into global variables (and hence into any shared perl library). Additionally under MULTIPLICITY, the perl executable now records the size of the interpreter structure (total, and for this version). Coupled with PL_bincompat_options this will allow 5.8.10 (and later), when compiled with a shared perl library, to perform sanity checks in main() to verify that the shared library is indeed binary compatible.

Symbolic references can now have embedded NULs. The new public function Perl_get_cvn_flags() can be used in extensions if you have to handle them.

Macro cleanups

The core code, and XS code in ext that is not dual-lived on CPAN, no longer uses the macros PL_na, NEWSV(), Null(), Nullav, Nullcv, Nullhv, Nullhv etc. Their use is discouraged in new code, particularly PL_na, which is a small performance hit.

New Tests

Many modules updated from CPAN incorporate new tests. Some core specific tests have been added:


Tests for the DynaLoader module.


Tests for compile-time constant folding.


Tests incorporated from 5.10.0 which check that there is no unexpected interaction between the internal types PVBM and PVGV.


Tests for the new form of constant subroutines.


Tests for Attribute::Handlers.


Tests for dbmopen.


Calls all tests in t/op/inccode.t after first tying @INC.


Tests for source filters returned from code references in @INC.


Tests for RT #30970.


Tests for RT #41484.


Tests for the qr// construct.


Tests for the qr// construct within another regexp.


Tests for the qr// construct.


Tests for RT #32840.


Tests for study on tied scalars.


Tests for subst run under -T mode.


Tests for undef and delete on stash entries that are bound to subroutines or methods.


Tests for Perl_sv_upgrade().


MRO tests for isa and package aliases.


Tests for calling Pod::Parser twice.


Tests for inheriting file descriptors across exec (close-on-exec).


Tests for the UTF-8 caching code.


Test that strange encodings do not upset Perl_pp_chr().


Tests for RT #40641.


Tests for RT #40641.


Tests for returning Unicode from overloaded values.


Tests for returning Unicode from tied variables.

Known Problems

There are no known new bugs.

However, programs that rely on bugs that have been fixed will have problems. Also, many bug fixes present in 5.10.0 can't be back-ported to the 5.8.x branch, because they require changes that are binary incompatible, or because the code changes are too large and hence too risky to incorporate.

We have only limited volunteer labour, and the maintenance burden is getting increasingly complex. Hence this will be the last significant release of the 5.8.x series. Any future releases of 5.8.x will likely only be to deal with security issues, and platform build failures. Hence you should look to migrating to 5.10.x, if you have not started already. Alternatively, if business requirements constrain you to continue to use 5.8.x, you may wish to consider commercial support from firms such as ActiveState.

Platform Specific Notes


readdir(), cwd(), $^X and @INC now use the alternate (short) filename if the long name is outside the current codepage (Jan Dubois).

Updated Modules

  • Win32 upgraded to version 0.38. Now has a documented 'WinVista' response from GetOSName and support for Vista's privilege elevation in IsAdminUser. Support for Unicode characters in path names. Improved cygwin and Win64 compatibility.
  • Win32API updated to 0.1001_01
  • killpg() support added to MSWin32 (Jan Dubois).
  • File::Spec::Win32 upgraded to version 3.2701


Updated Modules

  • OS2::Process upgraded to 1.03

    Ilya Zakharevich has added and documented several Window* and Clipbrd* functions.

  • OS2::REXX::DLL, OS2::REXX updated to version 1.03


Updated Modules

  • DCLsym upgraded to version 1.03
  • Stdio upgraded to version 2.4
  • VMS::XSSymSet upgraded to 1.1.


Nick Ing-Simmons, long time Perl hacker, author of the Tk and Encode modules, perlio.c in the core, and 5.003_02 pumpking, died of a heart attack on 25th September 2006. He will be missed.


Some of the work in this release was funded by a TPF grant.

Steve Hay worked behind the scenes working out the causes of the differences between core modules, their CPAN releases, and previous core releases, and the best way to rectify them. He doesn't want to do it again. I know this feeling, and I'm very glad he did it this time, instead of me.

Paul Fenwick assembled a team of 18 volunteers, who broke the back of writing this document. In particular, Bradley Dean, Eddy Tan, and Vincent Pit provided half the team's contribution.

Schwern verified the list of updated module versions, correcting quite a few errors that I (and everyone else) had missed, both wrongly stated module versions, and changed modules that had not been listed.

The crack Berlin-based QA team of Andreas König and Slaven Rezic tirelessly re-built snapshots, tested most everything CPAN against them, and then identified the changes responsible for any module regressions, ensuring that several show-stopper bugs were stomped before the first release candidate was cut.

The other core committers contributed most of the changes, and applied most of the patches sent in by the hundreds of contributors listed in AUTHORS.

And obviously, Larry Wall, without whom we wouldn't have Perl.

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 http://bugs.perl.org.  There may also be information at http://www.perl.org, 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 perlbug@perl.org to be analysed by the Perl porting team.  You can browse and search the Perl 5 bugs at http://bugs.perl.org/

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.

See Also

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.


2024-06-12 perl v5.40.0 Perl Programmers Reference Guide