return [ n ]
       Causes a shell function or `.' script to return to the  invoking
       script with the return status specified by an arithmetic expres-
       sion n. If n is omitted, the return status is that of  the  last
       command executed.

       If  return  was  executed from a trap in a TRAPNAL function, the
       effect is different for zero and non-zero return  status.   With
       zero  status  (or  after  an  implicit  return at the end of the
       trap), the shell will return to whatever it was previously  pro-
       cessing; with a non-zero status, the shell will behave as inter-
       rupted except that the return status of the  trap  is  retained.
       Note  that the numeric value of the signal which caused the trap
       is passed as  the  first  argument,  so  the  statement  `return
       $((128+$1))'  will  return  the same status as if the signal had
       not been trapped.