Library /sys$common/syshlp/BASICHELP.HLB

      SELECT exp1
             case-clause
                  .
                  .
                  .
             [ else-clause ]
      END SELECT

        case-clause:  CASE case-item,...
                      [ statement ]...

        case-item:    { [ rel-op ] exp2 }
                      { exp3 TO exp4    }

        else-clause:  CASE ELSE
                           [ statement ]...