use warnings;
use strict;
use XML::LibXML;
use Text::CSV;

my $dom = XML::LibXML->load_xml(location => 'example.xml');

my %items;
for my $product ($dom->findnodes('/products/product')) {
	my $sku = $product->findvalue('sku');
	for my $downloads ($product->findnodes('downloads')) {
		for my $group ($downloads->findnodes('group')) {
			for my $group_items ($group->findnodes('group_items')) {
				for my $item ($group_items->findnodes('item')) {
					my $name = $item->findvalue('name');
					my $url = $item->findvalue('url');
					$items{$sku}{$name} = $url;
				}
			}
		}
	}
}
my @columns = sort keys %{{map {$_=>1} map {keys %$_} values %items}};

my $csv = Text::CSV->new({binary=>1, auto_diag=>2, eol=>$/,
	always_quote=>1 });
$csv->print(select, ["sku", @columns]);
for my $sku (sort keys %items) {
	$csv->print(select, [ $sku, map { $items{$sku}{$_} } @columns ]);
}