[racket] raco-style command line parsing library?

Is there an alternative to the `command-line' form that supports the use of
raco-style (svn-style, cvs-style, etc.) command lines, where the first
argument is a subcommand, and each subcommand takes a different set of
arguments and options?

I know that in v4, planet had such a library, but it started with a
prominent disclaimer that it wasn't ready for prime time.  From what I can
see right now, raco uses ad-hoc logic to deal with this.

I'm in the process of writing something similar to the existing
`command-line' form that will handle this style of command line, and I
wanted to avoid duplicating effort.

Thanks,

Richard