You are viewing the version of this documentation from Perl 5.35.10. This is a development version of Perl.



perldelta - what is new for perl v5.35.10


This document describes differences between the 5.35.9 release and the 5.35.10 release.

If you are upgrading from an earlier release such as 5.35.8, first read perl5359delta, which describes differences between 5.35.8 and 5.35.9.

Core Enhancements

New function builtin::trim

This function treats its argument as a string, returning the result of removing all white space at its beginning and ending. See "trim" in builtin

Variable length lookbehind is mostly no longer considered experimental.

Prior to this release any form of variable length lookbehind was considered experimental. With this release the experimental status has been reduced to cover only lookbehind that contains capturing parenthesis. This is because it is not clear if


should match and leave $1 equaling "a" or "aa". Currently it will match the longest possible alternative, "aa". We are confident that the overall construct will now match only when it should, we are not confident that we will keep the current "longest match" behavior.

Added 'builtin::indexed'

A new function has been added to the builtin package, called indexed. It returns a list twice as big as its argument list, where each item is preceded by its index within that list. This is primarily useful for using the new foreach syntax with multiple iterator variables to iterate over an array or list, while also tracking the index of each item:

use builtin 'indexed';

foreach my ($index, $val) (indexed @array) {

Added experimental feature 'extra_paired_delimiters'

Perl traditionally has allowed just four pairs of string/pattern delimiters: ( ) { } [ ] and < >, all in the ASCII range. Unicode has hundreds more possibilities, and using this feature enables many of them. When enabled, you can say qr« » for example, or use utf8; <q𝄃string𝄂. See "The 'extra_paired_delimiters' feature" in feature for details.

Performance Enhancements

Modules and Pragmata

Updated Modules and Pragmata


Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes listed in this document. If you find any we have missed, open an issue at


The following additions or changes have been made to diagnostic output, including warnings and fatal error messages. For the complete list of diagnostic messages, see perldiag.

New Diagnostics

New Errors

Changes to Existing Diagnostics

Internal Changes


Perl 5.35.10 represents approximately 4 weeks of development since Perl 5.35.9 and contains approximately 15,000 lines of changes across 300 files from 26 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 6,900 lines of changes to 190 .pm, .t, .c and .h files.

Perl continues to flourish into its fourth decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.35.10:

Bernd, Brad Barden, Chad Granum, cuishuang, Curtis Poe, Dagfinn Ilmari Mannsåker, Daniel Laügt, Felipe Gasper, Graham Knop, Hugo van der Sanden, James E Keenan, Karl Williamson, Leon Timmermans, Matthew Horsfall, Michiel Beijen, Nicholas Clark, Nicolas R, Paul Evans, Renee Baecker, Ricardo Signes, Richard Leach, Sawyer X, Sisyphus, Steve Hay, TAKAI Kousuke, Yves Orton.

The list above is almost certainly incomplete as it is 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.

Many of the changes included 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.

Reporting Bugs

If you find what you think is a bug, you might check the perl bug database at There may also be information at, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at Be sure to trim your bug down to a tiny but sufficient test case.

If the bug you are 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 of how to report the issue.

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:


This will send an email to the Perl 5 Porters list with your show of thanks.


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.