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perldelta - what is new for perl v5.25.2


This document describes differences between the 5.25.1 release and the 5.25.2 release.

If you are upgrading from an earlier release such as 5.25.0, first read perl5251delta, which describes differences between 5.25.0 and 5.25.1.

Core Enhancements ^

Perl can now do default collation in UTF-8 locales on platforms that support it

Some platforms natively do a reasonable job of collating and sorting in UTF-8 locales. Perl now works with those. For portability and full control, Unicode::Collate is still recommended, but now you may not need to do anything special to get good-enough results, depending on your application. See "Category LC_COLLATE: Collation: Text Comparisons and Sorting" in perllocale.

Better locale collation of strings containing embedded NUL characters

In locales that have multi-level character weights, these are now ignored at the higher priority ones. There are still some gotchas in some strings, though. See "Collation of strings containing embedded NUL characters" in perllocale.

Lexical subroutines are no longer experimental

Using the lexical_subs feature no longer emits a warning. Existing code that disables the experimental::lexical_subs warning category that the feature previously used will continue to work. The lexical_subs feature has no effect; all Perl code can use lexical subroutines, regardless of what feature declarations are in scope.

CORE subroutines for hash and array functions callable via reference

The hash and array functions in the CORE namespace--keys, each, values, push, pop, shift, unshift and splice--, can now be called with ampersand syntax (&CORE::keys(\%hash) and via reference (my $k = \&CORE::keys; $k->(\%hash)). Previously they could only be used when inlined.

Security ^

-Di switch is now required for PerlIO debugging output

Previously PerlIO debugging output would be sent to the file specified by the PERLIO_DEBUG environment variable if perl wasn't running setuid and the -T or -t switches hadn't been parsed yet.

If perl performed output at a point where it hadn't yet parsed its switches this could result in perl creating or overwriting the file named by PERLIO_DEBUG even when the -T switch had been supplied.

Perl now requires the -Di switch to produce PerlIO debugging output. By default this is written to stderr, but can optionally be redirected to a file by setting the PERLIO_DEBUG environment variable.

If perl is running setuid or the -T switch has supplied PERLIO_DEBUG is ignored and the debugging output is sent to stderr as for any other -D switch.

Incompatible Changes ^

keys returned from an lvalue subroutine

keys returned from an lvalue subroutine can no longer be assigned to in list context.

    sub foo : lvalue { keys(%INC) }
    (foo) = 3; # death
    sub bar : lvalue { keys(@_) }
    (bar) = 3; # also an error

This makes the lvalue sub case consistent with (keys %hash) = ... and (keys @_) = ..., which are also errors. [perl #128187]

Modules and Pragmata ^

Updated Modules and Pragmata

Documentation ^

Changes to Existing Documentation







Diagnostics ^

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

Configuration and Compilation ^

Testing ^

Internal Changes ^

Selected Bug Fixes ^

Acknowledgements ^

Perl 5.25.2 represents approximately 4 weeks of development since Perl 5.25.1 and contains approximately 32,000 lines of changes across 430 files from 28 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 27,000 lines of changes to 300 .pm, .t, .c and .h files.

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 5.25.2:

Aaron Crane, Andreas König, Andy Lester, Chad Granum, Chase Whitener, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan Collins, David Mitchell, Dominic Hargreaves, Ed Avis, Father Chrysostomos, H.Merijn Brand, Ivan Pozdeev, James E Keenan, Jarkko Hietaniemi, Jerry D. Hedden, Jim Cromie, Karl Williamson, Lukas Mai, Matthew Horsfall, Misty De Meo, Samuel Thibault, Sawyer X, Sullivan Beck, Tony Cook, 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 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.

If the bug you are reporting has security implications which make it inappropriate to send to a publicly archived mailing list, then see "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details of how to report the issue.


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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