I'd like to refactor the following code:

    case @request.path
    when '/'
      Rack::Response.new do |response|
        do_stuff
      end
    when '/env' then Rack::Response.new(@env.to_html)
    end


And extract `Rack::Response.new`, something like the following:

    Rack::Response.new case @request.path
    when '/'    then Proc.new {|response| do_stuff }
    when '/env' then @env.to_html
    end

But I get

> stringable or iterable required

What's the correct implementation (Ruby 1.9.2)?