You can edit the response but you can't overwrite it:
~~~ php
<?php
// https://gist.github.com/3896743
$response = new stdClass();

echo '1): ' . spl_object_hash($response) . PHP_EOL; // 0000000021e89fcd00000000e93b17ba

call_user_func_array(function($response) {
	$response = new stdClass();
	echo '2): ' . spl_object_hash($response) . PHP_EOL; // 0000000021e89fcf00000000e93b17ba
}, array($response));

echo '3): ' . spl_object_hash($response) . PHP_EOL; // 0000000021e89fcd00000000e93b17ba

call_user_func_array(function($response) {
	$response = new stdClass();
	echo '4): ' . spl_object_hash($response) . PHP_EOL; // 0000000021e89fcf00000000e93b17ba // hash descoped and reused
}, array(&$response));

echo '5): ' . spl_object_hash($response) . PHP_EOL; // 0000000021e89fcf00000000e93b17ba
~~~

Otherwise you'd make the new response object and overwrite the values one at a time:
~~~ php
<?php
// https://gist.github.com/3897032
Route::filter('after', function($response)
{
	$params = \Laravel\Request::$route->parameters;
	// The 'type' is the last param
	// example: /product/(:num).(:any)
	$type = array_pop($params);
	if($type == 'json') {
		$res = Response::json($response->content->data);
		foreach($response as $key => &$value) {
			$response->$key = $res->$key;
		}
	}
});
~~~
Signed-off-by: Blaine Schmeisser <blaine.schmeisser@vitals.com>