The keyword return is used to return control flow from a procedure or function to its caller. For a procedure, the form "return;" (or the corresponding "(return)" for Lisps) is used, as there is no return value. For a function, the form "return value;" (or the corresponding "(return value...)" Lisp) is used.
Structured programming zealots note that return is an unstructured exit: there are potentially multiple returns, but only one entry point. For a procedure, there is always an alternate way to return control: just "fall off the end" of the procedure. Lisp and Perl extend this notion to functions, which are considered to return the last value computed before falling off. In C and its descendants, however, this is not allowed; a function must perform return value;, or the nasal daemons fly.