signal

(signal datum args...)

Signals a non-fatal condition with the same designator surface as error: a literal control string (builds a simple-condition), a quoted condition-type symbol with initargs, or a condition object. When a handler-case handler is established on the current thread of control the condition is raised to it; otherwise signal returns nil and execution continues (the Common Lisp fall-through). On the WASM backends there are no handlers, so signal always evaluates its arguments and returns nil. Lite: a raised signal that no clause of any established handler-case matches aborts like an error instead of falling through to nil.