ref: 03738c67684b83692d9112858f07c745f355a157
parent: a0eb2bb268774a85411f037983d931f35bc7830f
author: Peter Mikkelsen <peter@pmikkelsen.com>
date: Tue Jul 6 17:23:41 EDT 2021
Store the calling module in each goal, and fix a bug where unification could leave behind some bindings even though the unification failed.