How can I do unit testing in Perl?

I'd add my vote to picking up Test::More before going any further in Perl testing. The Perl testing community is fairly well united around the Test Anything Protocol, and you'll want to play around with Test::More to understand how it works and how tools like prove and Test::Harness::Archive can help automate and distribute testing.

If you want to just "jump right in", I think Test::Class provides xTest facilities with a TAP backend. I haven't used it at all (I'm a Test::More person myself), but it's very highly rated.

Test::More should offer you more bang for your bucks once you get the hang of Test::Simple.