Is Perl/Raku widely used these days? Are they worth learning? I've always been curious about those languages but I've had the impression that people are moving away from them.
I use raku mostly for fun. It has come a long way. It has further to go, but I don't mind. There is a surprising amount of vital packages already available for getting things done.
I don't think anyone believes perl5 will be as popular as it was years ago, or that raku will be a top-five language, but who cares? As long as the core community persists, its enough.
Perl may not be as popular now as it was in the past, but it is still around and lots of legacy systems that were written in Perl are still in active use.
If you find yourself in a place with frequent one-off text wrangling or Unix admin problems some Perl knowledge is worthwhile.
I find that regular expressions and text-wrangling tasks are faster and easier in Perl than in other programming languages due to its accessible syntax and regular expression engine speed.
This article shows the regular expression syntax in several popular programming languages: https://cs.lmu.edu/~ray/notes/regex/
This GitHub repo gives some regex performance test benchmarks: https://github.com/mariomka/regex-benchmark Perl is pretty fast among the scripting languages that were benchmarked.
If you are familiar with C / C++, then learning Perl is relatively fast and easy: https://perldoc.perl.org/perlintro
But as for usage, it's mostly legacy Perl codebases, which are much less interesting - Python and Ruby basically cover the same bases.
Only if your goal is to be able to work on legacy codebases. Learning a cool language in itself is cool.