Theorems about plist-worldp-with-formals (see the ACL2 source code).
Theorem: plist-worldp-when-plist-worldp-with-formals-cheap
(defthm plist-worldp-when-plist-worldp-with-formals-cheap (implies (not (plist-worldp wrld)) (not (plist-worldp-with-formals wrld))) :rule-classes ((:rewrite :backchain-limit-lst (0))))