Maintenance. I say this as somebody who loves Perl, quirks and all (actually because of the quirks). It's actually a beautiful language to work in in the same way English is a beautiful language -- it's a beauty because it's a goddamn mess. But it's a rotten language to maintain. Sure, it's perfectly possible to write highly maintainable code (I have a few 30-40k line Perl projects that I can open up and get right to…
I don't want the popularity we once had. The same people who wrote unreadable, unmaintainable perl went on to do the same sort of damage in PHP, then python, then ruby/rails, and now node.js/go. They were never a net positive to the community, and I'm not sorry to see them causing problems for somebody else. (and before somebody says "but that doesn't happen in X" ... yes, it does, even python lets you write code tha…
If someone really wants to use a language, there is no excuse for not reading a book for that language first.