"Perl 5 has been on the same major version for 30 years now"

I don't know that I would consider that accurate. 'Perl 5' is really no longer a version, but the language itself. It's had a lot of "major" releases over the last ~20 years and it's evolved significantly in that time. Sure, the language does prioritize backwards compatibility, but that is common among many programming languages. New features have been added regularly, however, and 'Modern Perl' brought around a lot of change in style and approach from the Perl of 30 years ago.