Prog challenge:

Write Ascii85 to binary converter in 10 lines of code.
Hard Mode: Using Python.
Hardcore Mode: in Esoteric language of your choice.

Still doesn't work perfectly (outputs characters at the end which should be truncated). Does Haskell classify as an esoteric language?

import Data.Char (chr, ord, isSpace)

dec5, decode :: String -> String
dec5 xs = map (chr . fromInteger) $ reverse $ map (flip rem 256) $ take 4 $ iterate (flip div 256) n
    where n = sum $ zipWith (*) (map (85^) $ reverse [0..4]) (map (\c -> toInteger $ ord c - 33) xs)

decode [] = []
decode s | head s == 'z' = (replicate 4 '\0') ++ (decode $ tail s)
         | isSpace $ head s = decode $ tail s
         | otherwise = (dec5 $ take 5 (s ++ cycle ['u'])) ++ (decode $ drop 5 s)