Perl's decline was cultural

I tried to learn perl a few times early in my career, we still had some old perl internal sites and a bit of tooling written in it. I really struggled to find good resources on the web at the time, and most of the perl I was exposed to was so badly written as to be incomprehensible to me. I knew C and Python at the time.

I wonder how common my experience was and why the next gen (at the time) I was part of never learned it

I had the exact same experience. The Perl I encountered early in my career seemed hard to understand in way other languages weren’t. I also didn’t feel I made progress quickly trying to learn it, every time I thought I had my feet under me I’d encounter a new sigil or a new pattern and be back to having no idea what the code was doing.