[perl #64288] 'my $x //= 42' leaves $x undefined

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
# Please include the string:  [perl #64288]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=64288 >


<szabgab> rakudo: my $x; $x//=42; say $x;
<p6eval> rakudo 370dd7: OUTPUT«42␤»
<moritz_> rakudo: my $x //= 42; say $x.perl
<p6eval> rakudo 370dd7: OUTPUT«undef␤»
<masak> heh.
<masak> bug.
<moritz_> masak: there's a job for you :-)
* masak does his job

Expected behavior: that the above two assignments behave the same.
More precisely, that the second one behave like the first one.