use Rack::CoffeeFilter::Filter, true to wrap.
You might think you want to use this gem. You could be wrong. It probably only makes sense for very small projects or in development.
Some rack servers (like Pow) serve files in /public statically. In those cases this gem won't do anything.
Add this line to your application's Gemfile:
In your config.ru
use Rack::CoffeeFilter::Filter # if you want to wrap the output in a function # use Rack::CoffeeFilter::Filter, true