It may well be. OTOH it doesn't seem to me to have ever suggested to use it "to teach people perl". Indeed golfing is for people who already do know perl.
Specifically, the OP wrote:
I'm looking for something fun that I can get these guys doing that will sharpen their perl skills.
Are there any games that get people programming in Perl?
Well, IMHO Perl golf is well suited for both. However this is controversial. The typical and most obvious objection on part of those who think this is not the case is that golfing techniques do not befit "serious" programming. My objection to this objection is that nobody ever claimed that they do and I bet that with at most a few isolated exceptions excellent golf players are also experienced programmers who can write "serious" code as well.
Yet golfing is instructive, for often the kind of optimizations applied there do not have to do only with dirty tricks like (ab)use of special variables and side effects that are normally avoided, but also with devising suitable algorithms for the problem under consideration. And in any case one is forced to deepen his perl knowledge...