[perl #123005] [BUG] $/ broken for replacement inside for loop

[via RT]

# New Ticket Created by   
# Please include the string:  [perl #123005]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=123005 >


my $a = 'a';
s/(.)/$0/ for $a;
$a.perl.say;

Expected result: "a"
Actual result: ""

This is perl6 version 2014.09-227-g3448cb1 built on MoarVM version 
2014.09-54-g03ac9a7