#!/usr/bin/perl

use strict;  # USE IT ALL THE TIME
use warnings; # USE IT ALL THE TIME
use Spreadsheet::WriteExcel;

my @model = qw (some random text goes here what else?);
my @processor = qw (some random text goes here what else?);
my @memory = qw (some random text goes here what else?);
my @softwareVersion = qw (some random text goes here what else?);
my @devicesPerVariant = qw (some random text goes here what else?);
my $devicePerModel = "Hello";

my $workbook = Spreadsheet::WriteExcel->new("test.xls") or die $!;
my $worksheet = $workbook->add_worksheet();
my $j = 0;
my $rowCounter = 1;   #### Declare rowcounter. O/W It is undef the first time around

$worksheet->write(0,0 , 'Equipment Model');
$worksheet->write(0,1, 'Devices Per Model');
$worksheet->write(0,2, 'Devices Per Variant');
$worksheet->write(0,3, 'Model Variant Processor');
$worksheet->write(0,4 , 'Device Memory');
$worksheet->write(0,5 , 'Device Software');


for ($j = 1; $j <= $#model; $j++)  {
    $worksheet->write($rowCounter,0, $model[$j]);

    ### You start with $j = 1 then why are you checking for this?????

    if ($j == 0) {
        $worksheet->write($rowCounter,1, $devicePerModel);
    }

    # Are you sure that all of your arrays have the same length?

    $worksheet->write($rowCounter,2, $devicesPerVariant[$j]);
    $worksheet->write($rowCounter,3, $processor[$j]);
    $worksheet->write($rowCounter,4, $memory[$j]);
    $worksheet->write($rowCounter,5, $softwareVersion[$j]);
    $rowCounter++;
}
$workbook->close();