doEval = function doEval(name) {
	var value;
	if (name === '%AsyncFunction%') {
		value = getEvalledConstructor('async function () {}');
	} else if (name === '%GeneratorFunction%') {
		value = getEvalledConstructor('function* () {}');
	} else if (name === '%AsyncGeneratorFunction%') {
		value = getEvalledConstructor('async function* () {}');
	} else if (name === '%AsyncGenerator%') {
		var fn = doEval('%AsyncGeneratorFunction%');
		if (fn) {
			value = fn.prototype;
		}
	} else if (name === '%AsyncIteratorPrototype%') {
		var gen = doEval('%AsyncGenerator%');
		if (gen) {
			value = getProto(gen.prototype);
		}
	}

	INTRINSICS[name] = value;

	return value;
}
Initialize a new `Router` with the given `options`.

@param {Object} [options]
@return {Router} which is an callable function
@public