Crypt::Enigma encrypts into a set found on an ordinary typewriter. But of course Enigma was cracked by the invention of the computer, which doesn't bode that well for security.

On the other hand you could pick one of the block cipher formats from the same namespace, say 128 or 256 bit, and just recode each nybble into hexadecimal (0-9 A-F) format for readability, using the unpack and pack functions to make the readable/unreadable transition, before or after the encode/decode depending on whether you are encrypting or decrypting.