Very definitely, you need to approach this from the point-of-view of “installing Perl as a non-root user” on a shared-hosting machine: one does not touch, for any reason, the native Perl installation or configuration on the host machine. You need to define your own local package repository, install your local versions of whatever-you-need there, and make very sure that nothing that you do (or consider doing) has anything to do with “root privileges.”
Mountain Lion, like Lion, changed the “native” Perl version. It’s a long way from both Leopard and Snow Leopard. (And for what it’s worth, I can tell you with authority that there are groups at Apple that were somewhat vexed by this.) So, you are quite comparing apples and oranges in this case.