Because it's not a regex flag, per se. It's a pattern matching operator flag. perlre only covers /i, /m, /s, and /x.
Jeff japhy Pinyan,
P.L., P.M., P.O.D, X.S.:
Perl,
regex,
and perlhacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart
I am starting to think that it may not be hung but searching for a long long time (many 10s of minutes). A product of the cascaded non-greedy searches failing at the last pattern. I will run it and see if it ever finishes. The file I am parsing is pretty small (few thousand lines) so it should finish if it can finish.