Hebigo will automatically expand Python reserved words to qualified macros. But we'll want some more "reserved" words than this. We also don't want them to conflict with normal Python identifiers. Thus far, Hebigo does not allow special characters in its symbols. So we can special case symbols that start with ! for this purpose.

At minimum, I think we'll need

• !let for locals
• !mask for quasiquotes
• !require for macro imports

Perhaps we should think of these as Hebigo's macro "builtins", in which case, we might want a lot more of them than this.