$format = $workbook->add_format(border   => 1);
for my $row (0 .. 2) {
    for my $column (0 .. 3) {
        $worksheet->write($row, $column,'undef',$format);
    }
}

##</code><code>##

$format = $workbook->add_format(border   => 1);
for my $row (1 .. 3) {
    for my $column ('A' .. 'D') {
        $worksheet->write($column.$row,'undef',$format);
    }
}