MGF discussion

# See https://www.reddit.com/r/ProgrammingLanguages/comments/1lguxx1/a_grammar_specification_language_idea/

say(add(42,99)); # 282                 # `add` calls `add` function.

sub add       (|args) { args.sum * 2 } # `sub add` declares `add` function.
sub infix:<+> (|args) { args.sum * 3 } # `sub infix:<+>` declares infix `+`.

say 42 + 99; # 423                     # `+` invokes infix op declared above.