Awful Haskell from http://www.reddit.com/r/haskell/comments/23pf6v/just_a_little_decider/, copied from the paste at http://lpaste.net/5303930864168599552. (I am not the author of this.)

interactive_sorting.hs

import qualified Data.Set as S
import System.IO.Unsafe
import System.Directory
import System.Environment
import Control.Exception
import Data.List

newtype Song = Song String
  deriving (Show, Read, Eq)

instance Ord Song where
  compare (Song a) (Song b) = unsafePerformIO $ do
    print "Which Song do you like better?"
    print $ "1. " ++ a
    print $ "2. " ++ b

    choice <- try readLn :: IO (Either SomeException Int)

    case choice of
      (Right 1) -> return LT
      (Right 2) -> return GT
      _ -> do
        print "invalid input, try again"
        return $ compare (Song a) (Song b)

main = do
  [path] <- getArgs
  c <- getDirectoryContents path 
  let songs = map Song $ filter (".gp5" `isSuffixOf`) c
  print $ S.toAscList $ S.fromList songs
  print "done"