Thankyou diotalevi++. That is exactly the sort of answer I was looking for and it confirms my suspicions based on some fairly dodgey benchmarking.
No matter how hard I tried to isolate the benefits of qr//'ing or /o'ing, those benefits always seemed to disappear whenever I attempted to combine one or more pre-compiled regexes with each other or with some non-compiled stuff. In fact, I sometimes detected a penalty from using pre-compiled regexes other than stand-alone, though the differences were too small to quantify with any accuracy.
Okay you lot, get your wings on the left, halos on the right. It's one size fits all, and "No!", you can't have a different color.
Pick up your cloud down the end and "Yes" if you get allocated a grey one they are a bit damp under foot, but someone has to get them.
Get used to the wings fast cos its an 8 hour day...unless the Govenor calls for a cyclone or hurricane, in which case 16 hour shifts are mandatory.
Just be grateful that you arrived just as the tornado season finished. Them buggers are real work.