Thank you all for your helpful advice.

@javafan: I was thinking the same but know no language-agnostic forum with such a concentration of people who are experts in all programming-related matters, who will assess a new problem quickly and precisely and who are very helpful. Besides, the site is built in Catalyst and I asked about existing solutions, which I would prefer in Perl.

@eric256: Since my site is just starting up and we have about ten regular users at this moment, I'll use the user flags as reports for admin-review. I'll be gathering the flagging actions and when I have a usable data sample, I'll try to machine-learn something from it.

If it turns out possible and worthwhile, I'll try to make a general tool out of this when it's ready.

Thanks to all for the insight once again... and happy new year! :-)