A fast C extension for parsing procedure arguments written by Cyan Ogilvie. Available from https://github.com/RubyLane/parse_args . Presented at the Tcl 2016 conference. See the paper (PDF) and slides .
AMG: argparse is remarkably similar, though currently implemented in Tcl script.
I wrote a long and detailed comparison between the two, but MSIE11 (which I am required to use because corporate policy claims it's more secure than Firefox or Chrome or anything else) crashed before I could hit save. I'll have to write it all again another time when I'm in a more stable environment.