Yes, it's worth it to learn Perl.

In my experience, the better I become at programming Perl, the better programmer I am in any of the other languages I know. This applies inversely as well - the better I get at programming other languages, the better I get at Perl. Part of it, it seems to me, is that by forcing yourself to think about things differently, you get better at problem solving - which is a very important trait for any programmer. You also expand the tools in your toolbox, by having Yet Another Possible Solution, which is never a bad thing. (I don't suggest building every solution using every language you know - the next person to maintain the software will hate you for it, for one thing.)

Learning is almost always worth it. In the case of programming, it's almost always a win-win situation. I'd even go so far as to advise you to try to learn (not master, of course, but get a decent grasp of) at least one language a year. There are plenty to choose from, and few of them are what I would consider to be "bad".