Its a very impressive show of one-liners, I love how expressive the language is. I wonder however, how easy it would be to extend compared to something like Lis

Its a very impressive show of one-liners, I love how expressive the language is. I wonder however, how easy it would be to extend compared to something like Lisp. If these idioms for parsing html weren't built-in, what would a Rebol implementation of those funcs look like?