do you know which col# is supposed to be a number?
i was thinking that you try something like this first:

if ( $col == 42 )
{
    $worksheet->write_number($row, $col++, $_);
}
else
{
    $worksheet->write($row, $col++, $_, $format);
}
[download]

and once you're sure 57 is coming back from your query into the sheet, then you can start playing around with $format and your regex