This is not in any way specific to Haskell, but I know a number of packages on Hackage have executables with command-line options, so: The non-Haskell program get_iplayer has an excellent idea for command-line options parsing. Rather than having to remember two separate syntaxes, one for command line options and one for a preferences file, the user can simply type get_iplayer --prefs-add --OPTION[=VALUE] which will add the equivalent of --OPTION[=VALUE] to the get_iplayer preferences file (and do nothing else). So it's like a special "preferences file manipulation mode" of the program. There are also the following options, as described by --help: --prefs-clear Remove *ALL* saved user or preset options --prefs-del Remove specified saved user or preset options --prefs-show Show saved user or preset options (This also means that the user doesn't have to remember the filename of the preferences file.) I think this sort of thing would be a good idea for *any* program that has command-line options that some user might want to hold constant across several runs. -- Robin