#!/usr/bin/perl
use strict;
use warnings;
use Excel::Writer::XLSX;

my $workbook  = Excel::Writer::XLSX->new( 'simple.xlsx' );
my $worksheet = $workbook->add_worksheet();

print "How many Serial Numbers do you need?\n";
my $mal  = <STDIN>;
my $comp = 'ITS';
my @array;

for (my $number = 1; $number <= $mal; $number++)
{
    my $exp = $comp . sprintf("%04d", $number);
    push @array, $exp;
}

$worksheet->write_col(0, 0, \@array);