module Main where

import Control.Applicative
import Control.Monad
import Data.Char

isLeftHandChar :: Char -> Bool
isLeftHandChar = (`elem` "qwertasdfgzxcvb") . toLower

isLeftHand :: String -> Bool
isLeftHand = all isLeftHandChar

main :: IO ()
main = do
  words <- lines <$> readFile "/usr/share/dict/words"
  forM_ words $ \w ->
    when (isLeftHand w) $ putStrLn w

Program error: /usr/share/dict/words: IO.openFile: does not exist (file does not exist)