FYI, the version of optparse-applicative (0.13.2.0) in Stack LTS-9.3 and earlier does not appear to handle the "noIntersperse" info modifier correctly. Instead of stopping parsing flags after the first non-option argument, it instead simply never parses any options. This is fixed in 0.14.0.0, which is in "Stackage Nightly". Perhaps someone else will run into the same issue. And it would of course be nice to see 0.14.0.0 appear in an upcoming LTS version (say 9.4). -- Viktor. Demo program, this fails to even process "--help" with the outdated optparse-applicative, which just reports all arguments as positional: module Main (main) where import Options.Applicative import Data.Monoid ((<>)) data Opts = Opts { bl :: Bool , fl :: Bool , st :: Maybe String , pos :: String , args :: [String] } deriving (Show) main :: IO () main = do let parse = Opts <$> switch ( long "bool" <> short 'b' ) <*> switch ( long "flag" <> short 'f' ) <*> optional ( strOption ( long "string" <> short 's' ) ) <*> strArgument ( metavar "FILE" ) <*> many ( strArgument ( metavar "ARGS..." ) ) i = info (helper <*> parse) $ fullDesc <> noIntersperse <> header "Option parser" <> progDesc "- test POSIX-style options" execParser i >>= print -- Viktor.