|Do you know where your variables are?|
I think your suggestion is really great for teaching programming with Perl, but it's not as good for teaching people how to use Perl effectively. Despite that statement, I do have mixed feelings about the whole thing, since I consider both to be very important. It is true, however, that it is impossible to master Perl per se without being able to use CPAN effectively.
You'll probably find that a lot of the monks disagree with you, but I think your post reflects some real thought. I also think that the nature of the Monastery, with its many opinions and opinionations will make sure that both the core language and CPAN are covered.
Don't forget that part of the reason the Monastery works so well is because people enjoy posting. Sometimes we get golf, but most of the time we get answers that really help. I suspect that requiring people to use the core language would be seen as unfun and discourage the plurality of paths to the same goal.