@(next :args)
@(cases)
@{key /[0-9]+/}
@text
@(or)
@  (throw error "specify <key-num> <text>")
@(end)
@(do
   (defvar k (int-str key 10)))
@(bind enc-dec
       @(collect-each ((i (range 0 25)))
          (let* ((p (tostringp (+ #\a i)))
                 (e (tostringp (+ #\a (mod (+ i k) 26))))
                 (P (upcase-str p))
                 (E (upcase-str e)))
            ^(((,p ,e) (,P ,E))
              ((,e ,p) (,E ,P))))))
@(deffilter enc . @(mappend (fun first) enc-dec))
@(deffilter dec . @(mappend (fun second) enc-dec))
@(output)
encoded: @{text :filter enc}
decoded: @{text :filter dec}
@(end)