-a            command-line option "a"
-b file       options can have arguments
              and long descriptions
--long        options can be long also
--input=file  long options can also have
              arguments

--very-long-option
              The description can also start on the next line.

              The description may contain multiple body elements,
              regardless of where it starts.

-x, -y, -z    Multiple options are an "option group".
-v, --verbose  Commonly-seen: short & long options.
-1 file, --one=file, --two file
              Multiple options with arguments.
/V            DOS/VMS-style options too
