$chart->add_series(
        categories    => xl_range_formula( 'Sheet1', 1, 9, 0, 0 ),
        values        => xl_range_formula( 'Sheet1', 1, 9, 1, 1 ),
    );



##</code><code>##

    $chart->add_series( categories => '=Sheet1!$A$2:$A$7'      ); # Same as ...
    $chart->add_series( categories => [ 'Sheet1', 1, 6, 0, 0 ] ); # Zero-index.