The "out of memory" issue is probably caused by Excel::Writer::XLSX. Especially if you have 1 million rows.

You can reduce its memory usage (almost completely*) by setting the workbook set_optimization() method.

    ...
    my $workbook = Excel::Writer::XLSX->new( file.xlsx' );
    $workbook->set_optimization();

    my $worksheet = $workbook->add_worksheet();
    ...
[download]

* See the Speed and Memory Usage section of the Excel::Writer::XLSX docs for a full explanation.

--
John.