I agree that it is most probably the Perl culture and of course the personal atmosphere that allows people to be open about their faith here. In places like ExpertExchange or SlashDot you'll probably see less declarations of faith, but it doesn't mean that there are less Christians there.
I don't think, however, that the Monastery metaphor has anything to do with it. In fact, the way it is used here, it doesn't have to do a lot with a monastery in the first place. The idea of "levels" and "XP" is more like the world outside the monastery... I also didn't start to learn Perl because Larry Wall is a Christian (I only heard later about that), but I think it is a good example that your faith of course is relevant: Larry's experiences with God clearly influenced the values he put into Perl. And these values made me stay with Perl.
I do think this is a very relevant topic -- not because being a Christian makes your code any different, but because being a Christian (should) make a difference in yourself, and of course this will show in your code and in your attitude towards others. There's not much sense in believing in God if you don't let him change your character...
I do have an aversion against the word "religion", since it conveys a lot of ideas that are contrary to a faith in Christ (at least in German). There's a lot of truth in what has been said, that programming languages and OSes can become religions as well. I prefer not to call myself religious, but rather a servant of Christ. The "official" term probably would be pentecostal, born-again Christian ;-)
So in real life, I am already a saint by grace, whereas on PerlMonks, I will be a saint by XP someday :).