(function caeser by of
  (let alphabets (proj (map char-code) (range 65 91) (range 97 123))
       shifted   (.. vec (map (rotate by) alphabets))
       table     (kv-dict (flatten alphabets) (flatten shifted)))
  (... str (map #(or (table %) %) of)))

(let original "The Quick Brown Fox Jumps Over The Lazy Dog."
     encrypted (caeser -1 original)
     decrypted (caeser 1 encrypted))
(str "Original:  " original "
Encrypted: " encrypted "
Decrypted: " decrypted)