   DISPLAY { literal-1    }... UPON { ENVIRONMENT-VALUE }
   ~~~~~~~ { identifier-1 }    ~~~~ { ~~~~~~~~~~~~~~~~~ }
                                    { ENVIRONMENT-NAME  }
                                      ~~~~~~~~~~~~~~~~
      [ ON EXCEPTION imperative-statement-1 ]
           ~~~~~~~~~
      [ NOT ON EXCEPTION imperative-statement-2 ]
        ~~~    ~~~~~~~~~
 [ END-DISPLAY ]
   ~~~~~~~~~~~