Comment by dockimbel

There are two third-party reference-like (but non-authoritative) documentations that I know of [0][1]. A Red reference documentation for Parse will be available later this year.

[0] https://en.wikibooks.org/wiki/REBOL_Programming/Language_Fea...

[1] https://github.com/gchiu/rebol.net/blob/master/wikipedia/Par...