PERL5403DELTA(1)

💖 PERL5403DELTA 💖

okay bestie, so this is the perl5403delta page — it's the tea on what's new in perl v5.40.3, and it lives in the Perl Programmers Reference Guide. pull up a chair, grab a boba, we're doing a release-notes deep dive 🫶

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✨ NAME ✨

perl5403delta — what is new for perl v5.40.3

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🌸 DESCRIPTION 🌸

so this doc spills the differences between the 5.40.2 release and the 5.40.3 release. that's it. that's the whole assignment 💅

and hey — if you're upgrading from something even earlier, like 5.40.1, you gotta read perl5402delta first, because that one covers the glow-up from 5.40.1 to 5.40.2. no skipping steps, bestie, the lore is cumulative 📚

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🔒 Security 🔒

[CVE-2025-40909] Perl threads have a working directory race condition where file operations may target unintended paths

okay so this one's serious, no cap. Perl thread cloning had a working directory race condition where file operations may target unintended paths. like, you'd think you're writing to one place and the vibes would take you somewhere else entirely. not it.

the fix: Perl 5.40 will no longer chdir to each handle. periodt.

this whole situation was discovered by Vincent Lefèvre via [GH #23010 <https://github.com/Perl/perl5/issues/23010>] and then assigned [CVE-2025-40909 <https://lists.security.metacpan.org/cve-announce/msg/30017499/>] by the CPAN Security Group <https://security.metacpan.org/>.

fixes came through via [GH #23019 <https://github.com/Perl/perl5/pull/23019>] and [GH #23361 <https://github.com/Perl/perl5/pull/23361>]. slay 🛠️✨

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💥 Incompatible Changes 💥

ngl there are no changes intentionally incompatible with 5.40.2. zero. none. if you find any, they're bugs, and we beg you to submit a report — see "Reporting Bugs" below. like genuinely, we want to know 🙏

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🧚 Modules and Pragmata 🧚

Updated Modules and Pragmata

• Module::CoreList got a glow-up from version 5.20250413_40 to 5.20250803_40. iconic behavior honestly 👑

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📖 Documentation 📖

Changes to Existing Documentation

we tried our best to update the docs so they reflect everything listed in this document. if we missed anything (and lowkey we might have), open an issue at <https://github.com/Perl/perl5/issues>. we're not mad, we just wanna know 💜

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🧪 Testing 🧪

tests were added and changed to reflect the other additions and changes in this release. testing era, fr fr 🧪✨

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🫶 Acknowledgements 🫶

Perl 5.40.3 represents approximately 4 months of development since Perl 5.40.2, and it contains approximately 3,400 lines of changes across 43 files from 7 authors.

and if we exclude auto-generated files, documentation and release tools? that's approximately 1,100 lines of changes to 6 .pm, .t, .c and .h files. the way that's so specific and yet so real 😭

Perl continues to flourish into its fourth decade thanks to a vibrant community of users and developers. (fourth decade!! main character energy for a language, honestly 👑) the following people are known to have contributed the improvements that became Perl 5.40.3:

Karen Etheridge, Leon Timmermans, Lukas Mai, Philippe Bruhat (BooK), Richard Leach, Steve Hay, Thibault Duponchelle.

just so you know — that list is almost certainly incomplete, because it's automatically generated from version control history. in particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker. we love you, mystery bug-reporters 🫶

many of the changes in this version originated in the CPAN modules included in Perl's core. we're grateful to the entire CPAN community for helping Perl to flourish. 💖

for a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

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🐛 Reporting Bugs 🐛

if you find what you think is a bug, you might check the perl bug database at <https://github.com/Perl/perl5/issues>. there may also be info at <https://www.perl.org/>, the Perl Home Page. 👀

if you believe you have an unreported bug, please open an issue at <https://github.com/Perl/perl5/issues>. and please — be sure to trim your bug down to a tiny but sufficient test case. tiny!! sufficient!! both!! that's the assignment 🎀

if the bug you're reporting has security implications which make it inappropriate to send to a public issue tracker, then see "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details on how to report the issue. stay safe out there 🔐

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🙏 Give Thanks 🙏

if you wish to thank the Perl 5 Porters for the work we had done in Perl 5, you can do so by running the perlthanks program:

perlthanks

this will send an email to the Perl 5 Porters list with your show of thanks. wholesome. we love a gratitude moment 🌈

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👀 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.

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and that's the whole page, bestie!! 🎀✨ this was perl v5.42.3, dated 2026-08-03 — so go forth, upgrade responsibly, and remember: the working directory is not a vibe, it's a contract 💅🦋