Personally, I view XP as a measure of a person's involvement with the PM community, not necessarily a measure of their Perl knowledge.

Most of my XP came from voting. Why don't I post more? Because I'm still learning Perl, so either I don't know the answer, or someone else has already provided one, and I have nothing to add (The posts where people re-iterate what someone else has already said really annoy me). So I vote instead, and make my small contribution to the PM community, and get my small reward in the form of an occasional XP point.

I would also imagine that if you take a look at how long that person has been a Perl Monks user, you'd probably find that they've been here a while. If someone's willing to 'hang around' that long, I think they should be given some XP. Without these people, PM wouldn't be such a strong site.