Palindrome Checker in Haskell

gistfile1.hs

import Data.Char
import IO

main = do
    fileName <- putStr "Enter the name of the file: " >> getLine
    contents <- readFile fileName
    mapM_  printOutput (lines contents)
    where
        getOutputMessage line = line ++ if isPalindrome line
                                        then " is a palindrome!"
                                        else " is NOT a palindrome!"
        printOutput line = putStrLn $ getOutputMessage (prepareLine line)

prepareLine = removeWhitespace . map toLower

removeWhitespace = filter (not . isWhitespace)
    where isWhitespace x = x `elem` " \t"

isPalindrome xs = xs == reverse xs

This needs an hFlush stdout