[perl #111720] [BUG] Subtle action-at-a-distance bond broken after seemingly innocent reading operation on array created with Array.new in Rakudo

[Christian Bartolomaeus via RT]

Post-GLR the read operation with $x.key[0] isn't necessary to get the buggy 
behaviour:

< bartolin>     m: my $x; my @a = 1,2; $x = Array.new(@a) => 'x'; @a.pop(); say 
$x;  # is that change with glr known/wanted
<+camelia>      rakudo-moar e6f360: OUTPUT«1 => x␤»
< GLRelia>      rakudo-moar a6bb0b: OUTPUT«[1 2] => x␤»
< bartolin>     m: my $x; my @a = 1,2; $x = @a => 'x'; @a.pop(); say $x;
<+camelia>      rakudo-moar e6f360: OUTPUT«1 => x␤»
< GLRelia>      rakudo-moar a6bb0b: OUTPUT«[1] => x␤»