});
// => displays each pair in turn
eachReference:
$numbers = [1, 2, 3];
_::eachReference($numbers, function (&$value) {
    $value *= $value;
});
// => [1,4,9]
map:
_::map([1, 2, 3], function ($value) {
    return $value - 1;
});
// => [0,1,2]
reduce:
$sum = _::reduce([1, 2, 3], function ($memo, $num) {
    return $memo + $num;
}, 0);
// => 6
reduceRight:
$list = [[0, 1], [2, 3], [4, 5]];
$flat = _::reduceRight($list, function ($a, $b) {
    return array_merge($a, $b);
}, []);
// => [4,5,2,3,0,1]
find:
$even = _::find([1, 2, 3, 4, 5, 6], function ($num) {
    return $num % 2 == 0;
});
// => 2
filter:
$evens = _::filter([1, 2, 3, 4, 5, 6], function ($num) {