ulrich@p0:~/scryer$ /opt/gupu/scryer-prolog/target/release/scryer-prolog -f
?- set_prolog_flag(occurs_check, error).\
.
caught: error(syntax_error(incomplete_reduction),read_term/3:2)
?- set_prolog_flag(occurs_check, error).
   true.
?- -X=X.
caught: error(representation_error(term),unify_with_occurs_check/2)
?- subsumes_term(-X,Y).
false.
?- [user].
subsumes_term(a,b).

false.