use strict;
use warnings;
use XML::Simple;
use Data::Dumper;

my $data = do {local $/;<DATA>};
my $xml  = XMLin($data);

print Dumper($xml), "\n\n";

for my $id (3,4) {
	print $xml->{gene}{$id}{'label'}, "\n";
}
__DATA__
<?xml version="1.0" ?>
<genes>
	<gene id = "3" label = "gene_of_interest" />
	<gene id = "4" label = "Another_gene_of_interest" />
</genes>

##</code><code>##

C:\test>220720
$VAR1 = {
          'gene' => {
                      '3' => {
                               'label' => 'gene_of_interest'
                             },
                      '4' => {
                               'label' => 'Another_gene_of_interest'
                             }
                    }
        };


gene_of_interest
Another_gene_of_interest

C:\test>