There is no reason to employ WWW::Mechanize. LWP::Simple is enough in this case. Though it doesn't seem to work for me ... I get a login page. So I can't have a look at the XML. There is also no need to remove the <?xml...> stuff.

As you do not seem to need the whole XML, you might you either XML::Twig or XML::Rules to process the XML in snippets. With XML::Rules you would just specify that the default rule is to forget the value of the tag (_default => '',) and the rule for 'srw_dc:dc' to print the 'dc:title' ('srw_dc:dc' => sub {print "$_[1]->{'dc:title'}\n"; return},).