You are making things up that do not at all match any kind of documentation. That's not how programming works.
The following code works for me, and all I needed to do was to read the documentation of XML::LibXML.
my $html_link = "http://rss.news.yahoo.com/rss/topstories";
my $dom = XML::LibXML->load_xml(location => $html_link);
my $xp = XML::LibXML::XPathContext->new($dom);
my @nodes = $xp->findnodes("/rss/channel/item");