As the great and powerful LanX said, it’s been discussed. What one language you should focus on is decided by far more than usage stats and Ruby/Python/Perl/Scala and others are quite similar on many level so learning one is a good jump on the others.

It matters where you live. Junior devs will generally never get (good) telecommute positions because they are competing with senior devs around the world.

It matters what your focus and comfort zone is. JavaScript is full stack now and on every device and with the slowburn of HTML5 and ES6 being adopted, it is an excellent place to invest in the near future. Other focuses like DB admin, sysadmin, testing… these jobs are readily available. Perl is a superior side-talent for most of them.

It matters what your cognitive bent is. Quite a few Perl hackers prefer Perl, warts and all, to all other languages because, as TheDamian once remarked, it allows you to hack how you think; no matter how you think.

It matters what your career goals are. Perl jobs are guaranteed if you have the skill or are in the right place—because there is a ton of Perl in the wild but fewer and fewer good Perl hackers—but Perl is more likely to evolve into a support, patch, or maintenance role. Not many greenfield projects in it. I work on a 20 year-old application and am paid rather well. It’s not much fun most of the time because it’s largely just making payments on technical debt and having the same argument about the cost of a rewrite every six months or so. That said, “not much fun” in Perl is a hundred times better than “not much fun” in Java, etc.