assertion failure/hang with / (?{(^{})/: perl 5.20 fix for review

Hi,

A Debian user reported a bug in the current stable release which I
bisected to f8a7ccebba5637bf0cf5a23cea563b2ccd62312d, authored by
Father Chrysostomos in October 2014. The Debian bug report is at:
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=825378>.

The user, Yuriy M. Kaminskiy, has provided a patch, which I have
attached to this email (note: it currently doesn't include any
backporting attribution). I'd welcome a review of this backporting
for correctness (though I appreciate that 5.20 is now out of support).

Cheers,
Dominic.

• assertion failure/hang with / (?{(^{})/: perl 5.20 fix for review by Dominic Hargreaves
• Re: assertion failure/hang with / (?{(^{})/: perl 5.20 fix forreview by Father Chrysostomos