First of all note that the proper venue for reporting issues with XML-LibXML is the rt.cpan.org queue as is linked from here - https://metacpan.org/release/XML-LibXML . Secondly, I'm pretty sure that XML-LibXML builds fine and passes its tests on perls newer than 5.16.x - I just ran "make disttest" with perl-5.20.1-8.mga5 on my x86-64 Mageia system and it told me that "All tests successful". The CPAN Testers Matrix also reports no problems with these perls - http://matrix.cpantesters.org/?dist=XML-LibXML+2.0121 .
So on account of these two thing, I'm going to reject this issue. If you can report a more specific symptom to the rt.cpan.org queue, that will be appreciated and please identify yourself.