Perl's decline was cultural

Perl's "decline" saved it from a fate worst than death: popularity and splitting into dozens of incompatible versions from added/removed features (like python). Instead Perl is just available everywhere in the same stable form. Scripts always can just use the system perl interpreter. And most of the time a script written in $currentyear can run just as well on a perl system interpreter from 2 decades ago (and vice versa). It is the perfect language for system adminstration and personal use. Even if it isn't for machine learning and those kinds of bleeding edge things that need constant major changes. There are trade-offs.

This kind of ubiquitous availablility (from early popularity) combined with the huge drop-off in popularity due to raku/etc, lead to a unique and very valuable situation unmatched by any other comparable language. Perl just works everywhere. No containers, no dep hell, no specific versions of the language needed. Perl is Perl and it does what it always has reliably.

I love it. The decline was a savior.

Perl's binary brings with it the ability to run every release of the language, from 5.8 onwards. You can mix and match Perl 5.30 code with 5.8 code with 5.20 code, whatever, just say "use v5.20.0;" at the start of each module or script.

By comparison, Python can barely go one version without both introducing new things and removing old things from the language, so anything written in Python is only safe for a a fragile, narrow window of versions, and anything written for it needs to keep being updated just to stay where it is.

Python interpreter: if you can tell "print" is being used as a keyword rather than a function call, in order to scold the programmer for doing that, you can equally just perform the function call.