Reddit reviews Effective Perl Programming: Ways to Write Better, More Idiomatic Perl (Effective Software Development) (Effective Software Development Series)

You'll see a lot of older Perl code out there.. view them, but don't use them as guidelines on how to write your own code. The Modern Perl book referenced earlier is a good place to get some insight into modern perl idioms.

I've also found the book Effective Perl Programming to be very lucid in giving a good lay of the land for the Perl language in general (explaining why things are, not just how to use them).

Your most valuable and ongoing learning vehicle will always be the CPAN. Every CPAN module available will have it's sources available too, and you can easily take a look at how some of the best perl programmers do their thing.

I really enjoy perl, it's been an endless discovery process for me. Once you actually "get it", you'll find it difficult to transition to anything else (for most tasks); because, regardless of the complexity of the given task, it simply lets you get stuff done.

Of course, don't let that stop you from learning other languages at the same time. Learning Javascript, for example, while learning Perl can have a serious, positive impact on your transferable skills down the road.

+1 to Effective Perl Programming. I'm convinced that it was reading the first edition of that was what turned me from someone who wrote a bit of Perl into someone who really understood how Perl worked.