I'm sure I knew about the optimization at some point, but it is just trivia to me. As I mentioned in another post, I haven't used ".." in a loop in several years. If I had needed that optimization I would have remembered it because figuring that out would have been a painful process (and there's nothing like several hours wasted to burn something into memory).

As for the stylistic differences, from the perlsyn docs (emphasis added):

The foreach keyword is actually a synonym for the for keyword, so you can use foreach for readability or for for brevity.