TBH, Perl being frozen in time isn't by design but rather a result of the extremely long (15+ years?) cycle of releasing Perl 6/Raku. In its heyday, Perl used to introduce new features and sigills all the time in dot versions. Also, I don't think Perl can claim the moral high ground on stability when the languages Perl was supposed to replace, such as awk, are POSIX-standardized and have multiple interworking implementations, and Perl even shipped an aggressive awk-to-Perl converter (a2p). As a legacy of Perl, PCREs with capture groups and above-regular language features invading environments and especially web frameworks and JavaScript also are of dubious value because of the attack vectors they bring.
The first version of PCRE was released in 1997, first Perl that supported PCRE in 2009. Claiming PCRE is "a legacy of Perl" is like saying C is a legacy of C#.
Calling a2p "aggressive" because it did a surprisingly good job converting awk to perl is like saying useful technology is aggressive.
Perl wasn't supposed to replace awk. It was designed to integrate features of C, shell, sed, and awk into one tool. That was spectacularly useful.
Perl is a high point in PL stability, still correctly running most Perl 4 scripts from the last century, with active community support for versions of Perl from 15 years ago. This is despite continuous evolution, eg adding Unicode support, in contrast to POSIX ("printable ASCII characters, space, BEL, backspace, tab, carriage return, newline, vertical tab, form feed, and null").
"Perl used to introduce ... sigills all the time in dot versions." Perl has never introduced a new sigil.
Perl maintains backwards compatibility despite also evolving because it's maintained by smart and conscientious professionals.
The OP discussion of the future is a continuation of that same philosophy.
Yeah on a second reading I didn't want to come down on Perl too harshly even though I still have memories of that moment where I had to listen to someone telling me "What, awk? We're doing Perl these days!" plus 3 not-so-pleasant projects over the years where we had to re-implement Perl systems.
OTOH there are a couple of Perl tools that I still use (or whish I'd still be able to use), and I'm grateful those exist and Perl 5 is being maintained: Norman Walsh's SGML DTD documentation generator, the old citeseer code base (infinitely more useful than it's today), Debian's apache a2enmod/a2ensite management tools (that I've partly rewritten in shell) and apt tools. I even wouldn't hesitate to use RequestTracker tools (ticket management over mail) today even though it might not scale all that well.
