that, then exit early. Called from :meth:`main` before the
program is invoked.

:param prog_name: Name of the executable in the shell.
:param complete_var: Name of the environment variable that holds
    the completion instruction. Defaults to
    ``_{PROG_NAME}_COMPLETE``.

.. versionchanged:: 8.2.0
    Dots (``.``) in ``prog_name`` are replaced with underscores (``_``).
NrĶ