"venire per.. (to come to ..)" takes a deliberate action (e.g. "he came to work" but not "he came to lose his bag")
"perdere (to lose)" is not deliberate - you don't intend to lose things.
working on caching serialized forms for faster copying
cache serialization of phrasal rules for speed
(fail? X) tests if X==:fail first, since this is (or should be) a common outcome of failed unification.
add unify namespace, with :excludes set to prevent collisions