It might be worth remembering that Perl's strength is amalgamating foreign cultures.

The distinction is not always clear either. If someone has a problem with their mod_perl stuff, they may not even be able to tell whether it's on the Apache end or the Perl side. Likewise someone's trouble with a database - and if it turns out to be something like a bug in a DBD it might even be arguable that it belongs to both sides of the fence.

Now don't think I'm advocating OT posts and broadening the focus - far from it. I'm firmly in favour of clearly labelling OT stuff as OT as a way of reinforcing the focus. But attempts to actively control OT stuff tend to drive down the very SNR you're concerned about as people start debating the merit of posts and the meta-ness of threads increases.

I've led a community before and learned a number of lessons in this area. The most important one is that rules cannot be enforced; they can only be suggested. Improving the quality of contributions does not happen by forbidding undesired content; it can only be brought about by making the community reinforce itself in encouraging desired content. This is a very indirect process that works ever better the fewer direct interventions happen. The articles you cite are a good place to start if you're interested in understanding these kinds of mechanics. :)

So all I'm saying is to remember that while Perl's the site's focus, that means there are other things on the blurry fringes of the picture. So long as people are reminded that these areas are off-focus, they will not divert their sight.