There are an enormous number of programming languages available on the market today, all of which seem to claim to be able to solve all your problems in half the time, at a quarter of the cost, and then bring about world peace, too. So why learn Perl over another one of those vaunted languages?
The best reason is that different tools work best for different tasks, and Perl is particularly good at a number of common tasks. But there are a number of other good reasons to learn and use Perl.
How's that for a good reason? Perl is probably the language for you if any of the following profiles describe you.
You're a system administrator looking for a general-purpose scripting language
You're a Web programmer with a dozen ...