LSUBR CONS and back-quote

[JLK at MIT-MC (John L. Kulp)]

I agree with RWK, and I bet MRG would agree also (judging by his code),
that code doing data structure construction using lists makes heavy
use of backquote outside of the context of macros.  I would also guess
it is used a lot less this way on the LISPM due to DEFSTRUCTs.