Active State, vs. Strawberry, is .. underneath the hood .. really a very different project from “ordinary ... e.g. Unix ... Perl.”   And you have just stumbled-upon one of those fundamental differences.   The AS designers took as their goal to make Perl very friendly to what they took to be their intended audience, which is IMHO a “mostly Windows(-only) aware” user community.   To accomplish this, they worked some magic, then rather buried that magic, and one of the places where they buried a lot of that magic is ppm.   So if you are told in-effect to “use that tool and don’t ask questions” ... :-D ... use that tool and don’t ask questions.   In particular, kindly forget entirely that cpan exists.   This is one of those situations where a very clever and resourceful design team cordially begs you to “ignore the little man behind that curtain over there.”   If you want to be using cpan you probably ought to be using Strawberry, because that’s more the philosophy that that project is intending to take.

IMHO, the Active State team and the Strawberry team looked at the same problem ... “how to bring Perl painlessly to Windows” ... and each team selected fundamentally different approaches to the same problem.   Both approaches are valid, but IMHO you will quickly sail down the wrong stream if you mix the two.