I started with perl and XML at the same time and I well remember how confusing the syntax of hashes was back then. It gets easier fast. Hopefully the code below will help clarify things.

A few things to note.

You need a root node in your xml. (I used <genes></genes>), this allows you to treat multiple lines as part of a single data structure. The root name will not show up in the Data::Dumper output. You don't use this as part of the structure reference.

You can use a variable/or a hardcoded string in the hash references.

Data::Dumper is very useful for understanding the structure returned by XML::Simple. Don't try it on a very large file of XML because it will churn for ages then run out of memory. Use it on small samples and then comment it out before testing your code on a large file. 

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>

[download]

Output

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>

[download]

Examine what is said, not who speaks.

In reply to Re: XML::Simple by BrowserUk
in thread How to access results of XML::Simple? by matth

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