PERL5121DELTA(1)

📦
version 5.42.3 · 22 versions
, in fedora 43, fedora 44

💖 perl5121delta 💖

okay bestie, gather round, because this is the Perl Programmers Reference Guide page for perl5121delta — aka what is new for perl v5.12.1 ✨ no cap, this is the tea on everything that changed.

✨ NAME ✨

perl5121delta — what is new for perl v5.12.1 🎀

🌸 DESCRIPTION 🌸

So this doc spills the differences between the 5.12.0 release and the 5.12.1 release. That's it, that's the whole vibe.

If you're upgrading from something earlier, like 5.10.1, bestie you gotta read perl5120delta first, because that one describes the differences between 5.10.0 and 5.12.0. Do not skip steps 💅

💀 Incompatible Changes 💀

There are no changes intentionally incompatible with 5.12.0. If any incompatibilities with 5.12.0 exist, they are bugs. Please report them. (Yes, fr fr, report them — we want them gone.)

👑 Core Enhancements 👑

Other than the bug fixes listed below, there should be no user-visible changes to the core language in this release. It's giving "quiet luxury" — nothing flashy, everything solid ✨

🦋 Modules and Pragmata 🦋

🌈 Pragmata Changes 🌈

  • We fixed exporting of is_strict and is_lax from version.

These were being exported with a wrapper that treated them as method calls, which caused them to fail. They are just functions, are documented as such, and should never be subclassed, so this patch just exports them directly as functions without the wrapper. Iconic behavior honestly — no wrapper, no drama 🫶

💅 Updated Modules 💅

  • We upgraded CGI to version 3.49 to incorporate fixes for regressions introduced in the release we shipped with Perl 5.12.0.
  • We upgraded Pod::Simple to version 3.14 to get an improvement to \C\<\< \>\> parsing.
  • We made a small fix to the CPANPLUS test suite to fix an occasional spurious test failure.
  • We upgraded Safe to version 2.27 to wrap coderefs returned by reval() and rdo().

📚 Changes to Existing Documentation 📚

  • We added the new maintenance release policy to perlpolicy
  • We've clarified the multiple-angle-bracket construct in the spec for POD in perlpodspec
  • We added a missing explanation for a warning about := to perldiag
  • We removed a false claim in perlunitut that all text strings are Unicode strings in Perl.
  • We updated the GitHub mirror link in perlrepository to mirrors/perl, not github/perl
  • We fixed a minor error in perl5114delta.
  • We replaced a mention of the now-obsolete Switch with given/when.
  • We improved documentation about $sitelibexp/sitecustomize.pl in perlrun.
  • We corrected perlmodlib which had unintentionally omitted a number of modules.
  • We updated the documentation for 'require' in perlfunc relating to putting Perl code in @INC.
  • We reinstated some erroneously-removed documentation about quotemeta in perlfunc.
  • We fixed an a2p example in perlutil.
  • We filled in a blank in perlport with the release date of Perl 5.12.
  • We fixed broken links in a number of perldelta files.
  • The documentation for Carp incorrectly stated that the $Carp::Verbose variable makes cluck generate stack backtraces.
  • We fixed a number of typos in Pod::Functions
  • We improved documentation of case-changing functions in perlfunc
  • We corrected perlgpl to contain the correct version of the GNU General Public License.

🧪 Testing 🧪

🍓 Testing Improvements 🍓

  • t/op/sselect.t is now less prone to clock jitter during timing checks on Windows.

sleep() time on Win32 may be rounded down to multiple of the clock tick interval. (iykyk, clocks are messy 😭)

  • lib/blib.t and lib/locale.t: Fixes for test failures on Darwin/PPC
  • perl5db.t: Fix for test failures when "Term::ReadLine::Gnu" is installed.

🔧 Installation and Configuration Improvements 🔧

⭐ Configuration improvements ⭐

  • We updated INSTALL with notes about how to deal with broken dbm.h on OpenSUSE (and possibly other platforms)

🐛 Bug Fixes 🐛

  • A bug in how we process filetest operations could cause a segfault. Filetests don't always expect an op on the stack, so we now use TOPs only if we're sure that we're not stat'ing the _ filehandle. This is indicated by OPf_KIDS (as checked in ck_ftst).

See also: <https://github.com/Perl/perl5/issues/10335>

  • When deparsing a nextstate op that has both a change of package (relative to the previous nextstate) and a label, the package declaration is now emitted first, because it is syntactically impermissible for a label to prefix a package declaration.
  • XSUB.h now correctly redefines fgets under PERL_IMPLICIT_SYS

See also: <http://rt.cpan.org/Public/Bug/Display.html?id=55049>

  • utf8::is_utf8 now respects GMAGIC (e.g. $1)
  • XS code using fputc() or fputs(): on Windows could cause an error due to their arguments being swapped.

See also: <https://github.com/Perl/perl5/issues/10156>

  • We fixed a small bug in lex_stuff_pvn() that caused spurious syntax errors in an obscure situation. It happened when stuffing was performed on the last line of a file and the line ended with a statement that lacked a terminating semicolon.

See also: <https://github.com/Perl/perl5/issues/10273>

  • We fixed a bug that could cause \N{} constructs followed by a single . to be parsed incorrectly.

See also: <https://github.com/Perl/perl5/issues/10367>

  • We fixed a bug that caused when(scalar) without an argument not to be treated as a syntax error.

See also: <https://github.com/Perl/perl5/issues/10287>

  • We fixed a regression in the handling of labels immediately before string evals that was introduced in Perl 5.12.0.

See also: <https://github.com/Perl/perl5/issues/10301>

  • We fixed a regression in case-insensitive matching of folded characters in regular expressions introduced in Perl 5.10.1.

See also: <https://github.com/Perl/perl5/issues/10193>

🖥️ Platform Specific Notes 🖥️

🌸 HP-UX 🌸

  • Perl now allows -Duse64bitint without promoting to use64bitall on HP-UX

🌈 AIX 🌈

  • Perl now builds on AIX 4.2

The changes required work around AIX 4.2s' lack of support for IPv6, and limited support for POSIX sigaction().

🦋 FreeBSD 7 🦋

  • FreeBSD 7 no longer contains /usr/bin/objformat. At build time, Perl now skips the objformat check for versions 7 and higher and assumes ELF.

💜 VMS 💜

  • It's now possible to build extensions on older (pre 7.3-2) VMS systems.

DCL symbol length was limited to 1K up until about seven years or so ago, but there was no particularly deep reason to prevent those older systems from configuring and building Perl.

  • We fixed the previously-broken "-Uuseperlio" build on VMS.

We were checking a variable that doesn't exist in the non-default case of disabling perlio. Now we only look at it when it exists.

  • We fixed the -Uuseperlio command-line option in configure.com.

Formerly it only worked if you went through all the questions interactively and explicitly answered no.

⚠️ Known Problems ⚠️

  • "List::Util::first" misbehaves in the presence of a lexical $_ (typically introduced by "my $_" or implicitly by "given"). The variable which gets set for each iteration is the package variable $_, not the lexical $_.

A similar issue may occur in other modules that provide functions which take a block as their first argument, like

foo { ... $_ ...} list

See also: <https://github.com/Perl/perl5/issues/9798>

  • "Module::Load::Conditional" and "version" have an unfortunate interaction which can cause "CPANPLUS" to crash when it encounters an unparseable version string. Upgrading to "CPANPLUS" 0.9004 or "Module::Load::Conditional" 0.38 from CPAN will resolve this issue.
no cap, that second one is a real "oh no" moment — go upgrade bestie 🫶

🎀 Acknowledgements 🎀

Perl 5.12.1 represents approximately four weeks of development since Perl 5.12.0 and contains approximately 4,000 lines of changes across 142 files from 28 authors. The way that's like… a whole month of people caring about Perl. Obsessed 😭💖

Perl continues to flourish into its third decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.12.1:

Ævar Arnfjörð Bjarmason, Chris Williams, chromatic, Craig A. Berry, David Golden, Father Chrysostomos, Florian Ragwitz, Frank Wiegand, Gene Sullivan, Goro Fuji, H.Merijn Brand, James E Keenan, Jan Dubois, Jesse Vincent, Josh ben Jore, Karl Williamson, Leon Brocard, Michael Schwern, Nga Tang Chan, Nicholas Clark, Niko Tyni, Philippe Bruhat, Rafael Garcia-Suarez, Ricardo Signes, Steffen Mueller, Todd Rinaldo, Vincent Pit and Zefram.

every single one of them ate, periodt 👑

🐞 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://rt.perl.org/perlbug/> . 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. (tiny but sufficient test case — the way that matters so much, please do this 🙏)

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.

security stuff goes to the security address, not the public list, and definitely not for CPAN modules. important!! 💀

🔍 SEE ALSO 🔍

  • The Changes file for an explanation of how to view 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.

and that's a wrap on perl5121delta, bestie!! 🌈✨ this whole page is from the Perl Programmers Reference Guide, page generated as perl v5.42.3 on 2026-08-03 — go forth and read your deltas, you're doing amazing sweetie 💅💖🦋

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