If you’re willing to take input on stdin, you can rewrite it without >>=: main = interact number where number = lines . zipWith addNumber [0.

If you’re willing to take input on stdin, you can rewrite it without >>=: main = interact number where number = lines . zipWith addNumber [0..] . unlines addNumber n l = show n ++ " " ++ l My point is that the logic itself does not require the idea of monadic sequencing — it’s relevant only for the minimal amount of surrounding IO.