My node had pretty good clues, actually. :P Try this–
use strict;
use XML::LibXML;
my $string = <<"";
<?xml version="1.0"?>
<ItemLookupResponse xmlns="http://webservices.amazon.com/AWSECommerceS
+ervice/2013-08-01">
<Items>
<Item>
<ASIN>B01KI4JSQY</ASIN>
</Item>
</Items>
</ItemLookupResponse>
my $doc = XML::LibXML->new->load_xml(string => $string, {no_blanks =>
+1});
my $xc = XML::LibXML::XPathContext->new($doc);
$xc->registerNs( x => $doc->getDocumentElement->namespaceURI );
for my $item ( $xc->findnodes('//x:ItemLookupResponse/x:Items/x:Item')
+ )
{
print $item->firstChild->nodeName, "\n";
print $item->firstChild->toString, "\n";
print $xc->findvalue('x:ASIN', $item), "\n";
}