As the previous answers show, hooking dynamic evaluation, or a subset thereof, into Haskell is not a particularly easy task. If this is just a program to get up-and-running with understanding Haskell, probably best not to delve into this sorts of stuff? A simpler solution, albeit one which requires some boilerplate, would be to ensure that either all the functions you dispatch to call getArgs themselves (i.e. are of type IO ()) or simply take a list of remaining parameters (i.e. are of type [String] ->IO ()) and then pull them out of either a list or a map. Something resembling this approach is, for example, here: http://haskell.org/haskellwiki/ Simple_unix_tools --S P.S. using Template Haskell to solve this would be a fairly interesting exercise as well, I suspect.