if turned on, it does strict variable references for 3x as well. It currently issues a warning with "Could not look up qualified variable" in 3.x - when the new option is on, it fails the operation. It is untested for 3.x (the error message is probably not very nice). We need to decide if it should remain separate, or always be strict in future evaluator and not apply to 3x. (Or if we want to use it in 3.x as well, make the error output nicer).