I pretty much agree to most of what been said, especially about the "sandbox" projects.
I would like to add, though, that since he is fresh from school, doing too much "scripting" stuff and exercises might fade his object oriented knowledge.
My suggestion is to encourage object oriented Perl solutions when possible, and anyway, to see that he uses the more advanced language features so the work isn't simply done, but a real Perl (and programming) experiance is gained.