[racket] Tagging data

I'm trying to use the language definition feature of Racket and one
thing I need to do is to distinguish primitive functions from those
defined in my module.  I'm imagining doing this by overriding lambda so
that it tags new functions as "non-primitive", but I can't think of a
way to do this (beyond, say, making a hash set of non-primitive
functions.  Is there any standard tool for "tagging" structures in
Racket?  Something like Clojure's metadata support?

Thanks in advance,
Pavel Panchekha