I don't feel I know enough yet about Perl.

I don't know that one can ever know 'enough'. Musing aside, you could check out online projects (google it) in your area of interest and try to code them. Not excercises in the traditional sense - no solutions - but something to let your brain chew on. :) The other suggestions so far seem much better than this one, but this will make you feel that what you are doing is "real life".