signal

(signal datum args...)

Signals a non-fatal condition with the same designator surface as error: a control string, literal or computed, with the arguments after it as its format arguments (builds a simple-condition), a quoted condition-type symbol with initargs, or a condition object. When an established handler-case has a clause matching the condition, the signal transfers control to it; otherwise -- no handler at all, or none whose clauses match -- signal returns nil and execution continues (the Common Lisp fall-through, CLHS 9.1.4.1). A handler-case whose clauses do not match is declined and stays armed for a later condition that does. This works on every backend except --no-gc, whose compiler rejects catching (signal there always evaluates its arguments and returns nil).