Perl is disliked because it has a very shallow learning curve to do badly, and a high learning curve to do well. Therefore, lots of people see a lot of bad code, but also people don’t understand a lot of good code.
Its the main reason any language is hated. JavaScript now is less hated because the tooling got there and people were educated at university to program in it well. PHP and Ruby are on the list of disliked on the SO analysis. Which is basically nonsense for modern versions of both languages. I really wish these stats would state "Perl 5" too, as Perl 6 is really modern in semantics and syntax and is nice to code in.
I agree that Perl 6 is the first readable version of Perl. It might actually be considered a nice language. Yet all the tools that are newly rewritten by our Perl guys are in Perl 5 because that's what they know.
Well not just what they know, but what all their existing stuff is written in. Makes sense too. The two Perls aren't really that compatible, far worse than migrating Python 2 to 3 and companies struggled with that manoeuvre. You can run and call each language from the other, with some in memory wrangling between https://github.com/niner/Inline-Perl5 But the same is true for Python and Java objects.