In my opinion, Perl is an unbeatable tool for solving the kind of problem where I want something done quickly and effectively. Yesterday I wrote a thingy that interfaces to a LDAP database, queries mySQL and in some cases does some HTML-scraping. It took me an hour to put it all together. I can't think about doing that in C, and I believe Java would have taken much more effort anyway.

Perl is very well suited to textual analysis, finding patterns and such stuff, and you can create data structures as complex as you like in a picosecond. Try Java for that and you'll see the difference.

Perl is also an expressive programming language, meaning that there is more than just machine efficiency in what you write. You can choose to explore a problem from many different points of view, quickly; a little functional here, a little object-oriented there, twenty lines of procedural glue, it all goes. No other language I know offers the same grade of expressiveness, and this is why I personally love the language.

If you take PHP, for instance, it's ok as long as you want to create web pages, but if in the matter you have to solve some programming tasks, it's often more a nuisance than a helpful tool. Perl is (nearly) always a nice environment to work in.

Warning: Personal rant follows:
What I don't like in Perl (in Perl 5, at least) is the way the language handles object-orientation; Java/C++ have a much better and cleaner syntax, and most other languages are following it (I have seen that PHP 5 will be almost word-by-word Java-alike). I see things are bound to change with Perl 6, and I hope I'll love that as much as I like the rest of the language....