Not sure why you got downvoted, but Rebol is not a Lisp. It doesn't work because of precedence rules or special rules, but because arguments accumulate until there are enough to eval the previous function in the stack, so you can do stuff like

  print tostring 5 + cos pi

Works a bit like a shift/reduce parser, with heavy use of fexprs (blocks in Rebol parlance)

I know you enjoy Lisps, so you might like this toy Rebol evaluator written in Scheme: http://ll1.ai.mit.edu/marshall.html