@(deffilter rot13
   ("a" "n") ("b" "o") ("c" "p") ("d" "q") ("e" "r") ("f" "s") ("g" "t")
   ("h" "u") ("i" "v") ("j" "w") ("k" "x") ("l" "y") ("m" "z") ("n" "a")
   ("o" "b") ("p" "c") ("q" "d") ("r" "e") ("s" "f") ("t" "g") ("u" "h")
   ("v" "i") ("w" "j") ("x" "k") ("y" "l") ("z" "m")
   ("A" "N") ("B" "O") ("C" "P") ("D" "Q") ("E" "R") ("F" "S") ("G" "T")
   ("H" "U") ("I" "V") ("J" "W") ("K" "X") ("L" "Y") ("M" "Z") ("N" "A")
   ("O" "B") ("P" "C") ("Q" "D") ("R" "E") ("S" "F") ("T" "G") ("U" "H")
   ("V" "I") ("W" "J") ("X" "K") ("Y" "L") ("Z" "M"))
@(repeat)
@line
@  (output :filter rot13)
@line
@  (end)
@(end)