Code:
var %text = http://localhost/#access_token=THIS_IS_WHAT_I_NEED&scope=channel_read+channel_editor+channel_subscriptions+channel_check_subscription
if ($regex(%text,/access_token=([^&]+)/)) {
  var %token = $regml(1)
}

Well. At least I won lunch.
Good philosophy, see good in bad, I like!