> example :: VoiceTwiml
> example =
>   response $ do
>     play (fromJust $ parseURL "https://api.twilio.com/cowbell.mp3") def
>     end
>   where Twiml.Syntax{..} = def

>>> show example
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Play>https://api.twilio.com/cowbell.mp3</Play>
</Response>