Parser is one of the show cases of the fundamental language approach to not have "code" and "data" but only have data, which might occasionally be interpreted using different parsers.

One example I don't think you can reproduce with macros is something like this (I don't have Red at hand)

    args: [x y]    # these are literal items, like quote in lisps
    code: [x * y]

    my_func: func args code
    print my_func 5 10    # prints 50