less.js/test/browser/runner-main-options.js

var less = {};
less.functions = {
    add: function (a, b) {
        return new(less.tree.Dimension)(a.value + b.value);
    },
    increment: function (a) {
        return new(less.tree.Dimension)(a.value + 1);
    },
    _color: function (str) {
        if (str.value === "evil red") { return new(less.tree.Color)("600") }
    }
};