> example :: VoiceTwiml
> example =
>   response $ do
>     dial "415-123-4567" def
>     say "Goodbye" def
>     end
>   where Twiml.Syntax{..} = def

>>> show example
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Dial>415-123-4567</Dial>
  <Say>Goodbye</Say>
</Response>