I think a better approach would be rooting out places in the site UI and documentation that give topic purists encouragement and making sure there is a site document clearly spelling out that "topics related to working with Perl are welcome", at least as a starting point.

Sanity! I still prefer the OT section solution; but a clear mandate that programming related subject on the fringes of being Perl-related would go a long way to mitigating for its absence.

And I agree with pretty much everything you said with regard to the need for some restrictions; and the areas where those restrictions are required.