Perl's decline was cultural

I'd take this a step further and say that the design flaws that motivated Perl6 were what really killed Perl. Perl6 just accelerated the timeline.

I do imagine a saner migration could've been done - for example, declaring that regexes must not start with a non-escaped space and division must be surrounded by space, to fix one of the parsing problems - with the usual `use` incremental migration.