YAOP is a library for options parsings that uses base GetOpt as a backend.

 {-# LANGUAGE TemplateHaskell #-}

 import System
 import System.Environment
 import System.Console.YAOP

 import Data.List
 import Data.Maybe

 -- | Options that are not mapped to data
 withoutData = dummy =: option [] ["action"] NoA "Do some action" (\_ _ -> putStrLn "IO Action")

 -- | Options data structure. Should use record syntax, may have more than one constructor
 data Options = Options { optFileName :: FilePath
                        , optCount :: Int
                        , optStuff :: [Either Int String]
                        } deriving (Show)

 -- | Default options
 defOptions = Options {optFileName = "default.txt", optCount = 0, optStuff = []}

 -- | This triggers YAOP's accessors generator, e.g.
 -- @modM_optFileName :: Monad m => (FilePath -> m FilePath) -> Options -> m Options@
 $(deriveModM ''Options)

 -- | Here we define a list of options that are mapped to Options
 optDesc = do
   modM_optFileName =: option ['f'] ["filename"] (ReqA "FN")
                       "Set some filename"
                       (\arg x -> print arg >> return (fromMaybe "" arg))
   modM_optCount    =: option ['c'] ["count"] (OptA "N")
                       "Set some count"
                       (\arg x -> return $ fromMaybe 100 (read `fmap` arg))
   modM_optStuff    =: option ['s'] ["stuff"] NoA
                       "Push \"foo\" to a list"
                        (\arg x -> return (Right "foo" : x))

 bothDesc = withoutData >> optDesc

 main = do
   (opts,args) <- parseOptions bothDesc defOptions defaultParsingConf =<< getArgs
   print opts
   print args