All procedures must end with END or RETURN.
When this command is entered during a procedure definition it tells VISTA
to leave the procedure-definition mode and to return to the
command-execution mode. The command is also saved in the procedure buffer
and signals the end of the current procedure when it is executed. If the
procedure is executed as a subroutine, the END command, like RETURN (q.v.),
tells VISTA to return to the calling procedure.