Most Perl texts have numerous exercises in them. I know the O'Reilly books do, and Dietel's book on Perl programming does to.
However if you're not excited by those, the best way ( I think ) to learn is do something you are interested in. Self projects are infinitely more interesting than excersises in books and you'll gain something useful when you're done and learn something in the process.
Failing that, drop me a note and I'll zip up the exercises from the Perl class I took if you would like.
Some people fall from grace. I prefer a running start...