Syntax:  SET PLACEHOLDER LEADING text_string defined_placeholder
              defined_language

  Identifies leading text to be associated with a placeholder.

  LSE recognizes this text and erases it when the associated
  placeholder is erased.  The leading text must not have any trailing
  blank spaces because the ERASE PLACEHOLDER command always skips over
  such spaces.

  RELATED COMMANDS:

     EXTRACT PLACEHOLDER         SHOW PLACEHOLDER
     NEW PLACEHOLDER