It's actually a trivial task. Try this:

#!/usr/bin/perl 

use strict;
use warnings;
use Spreadsheet::WriteExcel;

my $workbook = Spreadsheet::WriteExcel->new("Report.xls");
my $first    = $workbook->add_worksheet('Perl');
my $second   = $workbook->add_worksheet('Perl Flavours');
my $third    = $workbook->add_worksheet('ActivePerl');
my $fourth   = $workbook->add_worksheet('StrawberryPerl');
my $fifth    = $workbook->add_worksheet('VanilaPerl');

my $format = $workbook->add_format(
    center_across => 1,
    bold          => 1,
    size          => 10,
    border        => 4,
    color         => 'black',
    bg_color      => 'cyan',
    border_color  => 'black',
    align         => 'vcenter',
);

$first->set_column(0,0,20);
foreach my $worksheet ($workbook->sheets()) {
    $worksheet->write(0,0, "Perl", $format);
    $worksheet->write(1,0, "Perl FLAVOURS");
    $worksheet->write(2,0, "Active Perl");
    $worksheet->write(3,0, "Strawberry Perl");
    $worksheet->write(4,0, "Vanilla Perl");
}
$first->activate();
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