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# Knuth shuffle

```perl
sub shuffle (@a is copy) {
    for 1 ..^ @a -> $n {
        my $k = (0 .. $n).pick;
        $k == $n or @a[$k, $n] = @a[$n, $k];
    }
    return @a;
}
```

The shuffle is also built into the pick method on lists when you pass it a "whatever" for the number to pick:

```perl
my @deck = @cards.pick(*);
```