port select perl

[Jeremy Lavergne]

I was digging around in Ubuntu a bit the other day and noticed our `port select` equivalent, alternatives (8):
http://linux.die.net/man/8/alternatives

It follows a simple rule: if the version being installed is newer then the currently selected, update the symlinks. If it's older, don't change the symlinks.

Would this help us in handling multiple versions of perl, since it's a one-way automatic path?