> Perl 5 ... hasn't changed for 25+ years.

A major new version of Perl ships regularly. A few weeks ago the latest major new version shipped. From the 2025 changes document:

> Perl 5.42.0 represents approximately 13 months of development since Perl 5.40.0 and contains approximately 280,000 lines of changes across 1,600 files from 65 authors.

Skipping back 5 major new versions (to 2020):

> Perl 5.32.0 represents approximately 13 months of development since Perl 5.30.0 and contains approximately 220,000 lines of changes across 1,800 files from 89 authors.

2015:

> Perl 5.22.0 represents approximately 12 months of development since Perl 5.20.0 and contains approximately 590,000 lines of changes across 2,400 files from 94 authors.

2010:

> Perl 5.16.0 represents approximately 12 months of development since Perl 5.14.0 and contains approximately 590,000 lines of changes across 2,500 files from 139 authors.

There's been well over 10 million lines of code changed in just the core Perl codebase over the last 25 years reflecting huge changes in Perl.

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Perl 6 ... isn't backward compatible

Raku runs around 80% of CPAN (Perl modules), including ones that use XS (poking into the guts of the Perl 5 binary) without requiring any change whatsoever.

(The remaining 20% are so Perl 5 specific as to be meaningless in Raku. For example, source filters which convert Perl 5 code into different Perl 5 code.)

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But you are right about one thing; no one you know cares about backwards compatibility, otherwise you'd know the difference between what you think you know, and what is actually true.