モナドが絡んで訳のわからないことに…

TextRegex.hs

import Text.Regex.Posix
main = do name <- getLine
	  print (checkURL name)
          print (countURLLength name)
	  print (twitLength name)
          checkLengthAndTwit name

-- URLの正規表現を定める
urlRegex :: [Char]
urlRegex = "(https?|ftp)(://[-_.!~*\'()a-zA-Z0-9;/?:@&=+$,%#]+)"

-- t.coのURL長
tcoLength :: Int
tcoLength = length "http://t.co/xxxxxxx"

-- その文字列、URLですか？
checkURL url = ( url =~ urlRegex ) :: String

-- URLの文字数をカウント
countURLLength :: [a] -> Int
countURLLength url = length url

twitLength :: [a] -> Int
twitLength str = (length str) - (countURLLength str) + tcoLength

twitLength' str = if 0 < (countURLLength str) then
                     return () >> return ((length str) - (countURLLength str) + tcoLength)
                  else return() >> return (length str)
-- 文字数のチェック
-- TODO:URLの文字数カウント
-- checkLengthAndTwit :: [Char] -> IO ()
checkLengthAndTwit msg
 | 0 == twitLength msg = putStrLn "at least 1 character!"
 | 140 < twitLength msg = putStrLn "over 140 characters!!"
 | otherwise = print msg