I don't really buy that. We don't have to satisfy every possible installation requirement in PREFIX. We document what it does, and we leave it at that. It sets the root directory. You only get to do that once. Whatever you set is what you get. As for it's actual effect between MakeMaker versions 5.x and 6.x, who's fault is that, eh? :)
If the documented PREFIX doesn't work for you, you don't use PREFIX. However, it works for a lot of people who aren't so picky about such things.
One of the key talents in a software developer is knowing when to stop letting the user have flexibility. That's one way to make code much simpler: just say "You can't use this for everything".
brian d foy <email@example.com>