#!/usr/bin/perl
use warnings;
use strict;

use XML::LibXML;

my $xpc  = XML::LibXML::XPathContext->new();
my $xml  = XML::LibXML->load_xml(IO => *DATA);
my $root = $xml->documentElement;
$xpc->registerNs('xlink', 'http://www.w3.org/1999/xlink');
my $chapter_node = $xpc->findnodes('book:chapter', $root)->[0];
print $xpc->findvalue('book:locator/@xlink:title | book:locator/@xlink:href', $chapter_node) . "\n";