It won't be exposed as a special form - rather it will be exposed as a bytecode, and the symbolcode-to-bytecode compiler will be exposed as a function that the implementation specific '$ will return. This should reduce the conceptual footprint of extensions to Arc that I add strictly for efficiency, versus actual axioms.
Basically we just grab $ as a sort of dispatcher for implementation-specific stuff (much like it is used to access mzscheme in Anarki), and put anything that is more-or-less implementation-specific there.
