Within all the various replies, in regards to implementing rot13 in this clunky way, the "you're doing it wrong" message has come through loud and clear (I hope). This is almost certainly an XY question.

I'm thinking of the future Super Search-er who does want to make use of his many and varied Python dictionaries in Perl scripts (now that he has seen the light). I hope he will find what he needs in this thread as well.