Hans Aberg writes:
 > >(or according to Hans - I need more convincing):
 > >
 > >  \hierarchical/path/to/module/perhaps_with
 > >      _underscores/macro_name:argspec:
 >
 >   The only point with a terminating ":" would be to make it easier
 > to know where the argspec ends if one processes the command
 > name. This could be done otherwise by a convention that the argspec
 > can only occupy one letter, or if that does not give sufficiently
 > many combinations, that if the first letter is uppercase it is a
 > two letter argspec, or something.

Hmm . . . at this stage let's say that an argspec can only contain
A-Z and a-z.  Then the argspec is the longest contiguous sequence of
letters after the colon - easily specified with a regular expression.