Welcome back!

"what's the policy on StackOverflow cross posts?"

You did just fine :) Personally, I'd prefer to see a link to the cross-posted post within the message body here (same goes for over at SO I would assume), but just making note of it is far, far better than nothing, and imho, acceptable.

I'm not familiar with Parse::RecDescent, so I'll have to leave that up to the more experienced Monks for that question.

Update: far better response by anonymonk above: Cross-posting Policy?.