$format = $workbook->add_format(border   => 1);
    $worksheet->write('A1:D3',$format);
##</code><code>##

    $format = $workbook->add_format(border   => 1);
    $worksheet->write('A1','undef',$format);
    $worksheet->write('B1','undef',$format);
    $worksheet->write('C1','undef',$format);
ect