Searches the internal database for a term recorded under the key Key that unifies with Term, and whose database reference unifies with Ref.
If Ref is instantiated, then Key and Term
are unified with the key and term associated with Ref.
Otherwise, If Key is a compound term, only its principal functor is
significant. That is,
foo(1) represents the same
Can be used to backtrack through all the matching terms recorded under the specified key.