Steven Mackenzie wrote: composing: If you gather options from several places such as the command line, system-wide options file, user-specific options file and so on then the tokens gathered from different places will be combined and together they form the final option value. Without the composing property only the first definition encountered will be taken as the value. zero_tokens: As I understand, this property is used with flags that don't get any arguments such as -v [--version] could be. multiple_tokens: For example a string option -E could be given like this: program -E stuff more_stuff even_more_stuff -- file now the value of option -E will be "stuff more_stuff even_more_stuff". Without the multiple_tokens property -E would be just "stuff" and all the other stuff would be given as positional options (and probably fail). niko