state_vars_test2.m:018: Warning: the condition of this if-then-else cannot
state_vars_test2.m:018:   fail.
state_vars_test2.m:019: Error: state variable !:Y is not visible in this
state_vars_test2.m:019:   context.
state_vars_test2.m:019: In clause for predicate `p'/2:
state_vars_test2.m:019:   warning: variable `Y' occurs only once in this scope.