Array splicing with coffeescript, what is _ref for?
===

In the CoffeeScript docs for [array splicing][1], what is the purpose of the trailing `, _ref`?

CoffeeScript:

    numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    numbers[3..6] = [-3, -4, -5, -6]

Compiles to:

    var numbers, _ref;
    numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
    [].splice.apply(numbers, [3, 4].concat(_ref = [-3, -4, -5, -6])), _ref;


  [1]: http://coffeescript.org/#slices