Perl can be used in a lot of ways. For me, I like to use it to quickly hack up a script to process some data in some way real quickly. I've used it to take a directory full of pictures, and generate a static HTML photo album with thumbnails and everything (invoked imagemagick).

Once you get good at it, and once you get pretty comfortable with grep/map, you can do some really nice stuff with it really quickly. I just use it as a "quick-n-dirty" tool, though. I'm of the opinion that it's generally not a good idea to do BIG things with it (though it CAN be done... just... ugh maintenance nightmare).