Availability:built-in
unifiable(@X, @Y, 
-Unifier)If X and Y can unify, unify Unifier 
with a list of
Var = Value, representing the bindings required to 
make X and Y equivalent.62This 
predicate was introduced for the implementation of dif/2 
and when/2 
after discussion with Tom Schrijvers and Bart Demoen. None of us is 
really happy with the name and therefore suggestions for a new name are 
welcome. This predicate can handle cyclic terms. Attributed 
variables are handled as normal variables. Associated hooks are not 
executed.