Ruby: Basic Rack app with env and lambda

config.ru

class RackApp
  def call(env)
    [200, {"Content-Type" => "text/html"}, ["Hello Rack! - you requested #{env["REQUEST_PATH"]}"]]
  end
end

run RackApp.new

# lambda.call -- rack uses .call
#run lambda { |env| [200, {"Content-Type" => "text/html"}, [env.to_s]] }