[perl #131102] [REGRESSION] anonymous variables are no longer working as expected in regex code blocks

[via RT]

# New Ticket Created by  Aleks-Daniel Jakimenko-Aleksejev 
# Please include the string:  [perl #131102]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=131102 >


Code:
(^10).grep: /^ <?{ say $++ }> /

Result (2015.12,2016.10):
0
1
2
3
4
5
6
7
8
9

Result (2016.11,HEAD(099512b)):
0
0
0
0
0
0
0
0
0
0


Bisectable points to 
https://github.com/rakudo/rakudo/commit/7a456ff80183a6e26dc91d811d992112c68ddb6d