[racket-dev] Where might I find undocumented un-greppable primitives?

(open-input-file file-name)
=maacrooooos=>
(let ((file-name1 file-name))
               (if (variable-reference-constant? open-input-file6)
                 (open-input-file4 '#f '#f file-name1)
                 (open-input-file6 file-name1)))

These identifiers are nowhere. I imagine these will be the first of many crazy things I'll run into during my implementation.

What/where are they? I'm trying to make a sound analysis/small step semantics here.
Thanks,
-Ian