Alternative Completion
======================
compctl [ -CDT ] OPTIONS + OPTIONS [ + ... ] [ + ] COMMAND ...
The form with `+' specifies alternative options. Completion is tried
with the options before the first `+'. If this produces no matches
completion is tried with the flags after the `+' and so on. If there
are no flags after the last `+' and a match has not been found up to
that point, default completion is tried. If the list of flags contains
a -t with a + character, the next list of flags is used even if the
current list produced matches.