I tried compiling XML::LibXML from CPAN using instructions that included making zlib1.dll, iconv.dll and xmlm2.dll in your path or else use the command
perl Makefile.PL INC=-Ic:\perl_libxml\include LIBS=-Lc:\perl_libxml\lib
It failed to compile with a dmake error 129 about xmlm2.dll. I assume that I was using a version of xmlm2.dll incompatible with XML::LibXML 2.0121.
In the end I found the only alternative ActivePerl repository in existence, as far as I can tell, and it had a package for XML::LibXML 2.0121 which will install on perl versions up to 5.20.x.
You can obtain releases of ActivePerl from here that includes 5.20.2: http://downloads.activestate.com/ActivePerl/releases/
The alternative repository is called Bribes de Perl at bribes.org/perl/
The URL of the repository that is entered in ActivePerl options is http://bribes.org/perl/ppm/