If you're running Windows, you can get a binary build of XML::LibXML from Randy Kobes' PPM repositories. If you're running Linux then things will be even simpler - just use the package from your distribution (eg: on Debian: apt-get install libxml-libxml-perl).
Sadly, with Randy Kobes passing, the Kobes repository has been rather unmaintained (is there no one at U Winnepeg that can step up?? Please??). Fortunately, Strawberry Perl comes with XML::LibXML, although I'm not sure how easy it is to make updates to the library.
Update: It looks like there is a version in ActiveState's repo, though kind of old.