At a guess I'd say that the $worksheet object has been garbage collected before you try to use it in colcmp():

    sub colcmp {
        ...
        $worksheet->write_rich_string($comp_row, $col->[0], join(",", 
+@wmap));
    }
[download]

You can verify that by adding a $workbook->close() to the end of your program.

--
John.