[perl #120704] [BUG] Chained assignments occasionally get screwed up

[via RT]

# New Ticket Created by  Rob Hoelz 
# Please include the string:  [perl #120704]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=120704 >


There's a bug such that the following doesn't work as expected:

  my $value = @!values[0] = @!values.pop;

-Rob
use v6;
use Test;

plan 1;

class BinaryHeap {
    has @!values = (84, 85);

    method push($value) {
        fail 'I should never be called!';
        # commenting this line out fixes the problem (note how this method is 
never called?!?!)
        @!values[0] = 1;
    }

    method pop {
        my $result = @!values[0];

        if @!values == 1 {
            @!values.pop;
        } else {
            # changing this line...
            my $value = @!values[0] = @!values.pop;
            # ...to this fixes the problem
            #my $value = @!values.pop;
            #@!values[0] = $value;
            is $value, @!values[0], '$value and @!values[0] should be equal';
        }
        $result
    }
}

my BinaryHeap $heap .= new;
$heap.pop;
$heap.pop;