like assoc-equal but does not cause an error.
Major Section:  HONS

Hash-Cons'ed association lists used with HONS-GET, HONS-ACONS, and HONS-ACONS!, may have any symbol at the end instead of just NIL, as ALISTP requires. The symbol allows an association list to be 'named'. Such naming may be important to keep fast hash alists from colliding with one another, resulting in inefficient performance.