[perl #61902] [BUG] r34778 - strange list happenings

[Mark A. Hershberger]

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I was working on Euler problem 2
(http://projecteuler.net/index.php?section=problems&id=2), trying to set
up a Fibonacci class when I discovered the following strange behavior.
The code to my solution works under Pugs and produces the following
output:

    2,8,34,144,610,2584,10946,46368,196418,832040,3524578
    4613732


Under rakudo, I get the following output:

    Use of uninitialized value
    (repeated several times — the warning comes from the first line in the 
next() method)
    
5702887,5702887,5702887,5702887,5702887,5702887,5702887,5702887,5702887,5702887,5702887
    62731757

Here's the source:

-=-=- cut -=-=-
#!perl6

class Fibonacci {
  has @!list is rw = (0, 1);

  method next() {
    @!list[2] = [+] @!list;
    shift @!list;
    return @!list[1];
  }
}

my $fibber = Fibonacci.new;
my $f;

my @r = gather {
  $f = $fibber.next;
  while($f < 4000000) {
    take $f if $f % 2 == 0;
    $f = $fibber.next;
  }
}
say @r.join(",");
say [+] @r;