Perl can do CGIs, even though PHP is simpler.

Perl can do OOP, even though Python and Ruby are cleaner.

Perl can do text processing, even though sed/awk/yacc/grep are more specific to the task.

Perl can process XML, even though XSLT is (arguably) superior.

But none of these languages can do all these things reasonably well. This is what people sometimes miss when they say "Use the best tool for the job!" (and why I tend to avoid that phrase). If your task is simple, then you can get away with using a very specific tool for your task. In anything bigger, you're going to need to do a wide range of tasks. While you can break your complex task into several simple ones, you still need some way to glue together each part. For the purposes of getting real work done, you often need to pick just one tool, because trying to put many domain-specific tools together isn't worth the effort. You're often better off picking a tool which can do it all reasonably well rather than twenty tools that do very specific tasks.

There's a reason why Perl is called the Swiss Army Chainsaw.

Update: Speeling mistake. Thanks tilly.