use strict;
use warnings;

use XML::Twig;

my $xml = <<XML;
        <reference>
        	<authors>
            		<author>Lindsley, O.R.</author>
            	</authors>
   
        	<year>1992</year>
       
        	<title>Precision teaching:  Discoveries & effects.</title>
       
        	<source>Journal of Applied Behavior Analysis</source>
   
        	<volume>25</volume>
        	<pages>51-57</pages>
        </reference>
XML

my $twig = new XML::Twig();
$twig->parse($xml);