dissoc

(dissoc m k ...)

Answers a fresh map over m's pairs minus the given keys; absent keys are ignored and m is never mutated. dissoc of nil is nil. Of a record the type survives while every declared field is still present and drops to a plain map otherwise, like the oracle.

As a value a map plus a rest list of keys.

Deviation: transients (dissoc!) are refused by name. Misuse of a non-map may signal the Common Lisp type error instead of the oracle's.