Syntax:  SET PLACEHOLDER TERMINAL LINE body_string add_remove
              defined_placeholder defined_language

  Specifies a line of a terminal-type placeholder.

  This body of a terminal placeholder appears in a separate temporary
  buffer when the placeholder is expanded.  The placeholder is not
  replaced in the current buffer.  This command is valid only for
  terminal-type placeholders.

  RELATED COMMANDS:

     EXTRACT PLACEHOLDER         SHOW PLACEHOLDER
     NEW PLACEHOLDER