[perl #77054] rakudo doesn't like explicit $_ in multi-param signatures

[via RT]

# New Ticket Created by  Moritz Lenz 
# Please include the string:  [perl #77054]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=77054 >


21:53 < moritz_> rakudo: for <a b>.kv -> $k, $_ { .perl.say }
21:53 <+p6eval> rakudo 0e5edb: OUTPUT«0␤1␤»
21:53 < moritz_> huh.
21:54 < moritz_> shouldn't that be "a", "b" ?
21:54 < moritz_> rakudo: for <a b>.kv -> $k, $v { $v.perl.say }
21:54 <+p6eval> rakudo 0e5edb: OUTPUT«"a"␤"b"␤»

I don't see why it shouldn't work with $_ if it works with $v.