How can I access ruby instance variable from within coffeescript template?

In sinatra documentation it's said that templates are evaluated within same scope as rout that invoke that template.

So, I have following sinatra app:

**server.rb**:

```
require "sinatra"
require "coffee-script"

get '/app.js' do
  @str = "Hello"
  coffee :app
end

```

and in views/app.coffe file I would like to use `@str`variable. Is it possible? If so, how can I access `@str` variable?