anchor.diff:  
     recognize(env).each do |route|
       env['eldr.route'] = route
  -    params.merge!(route.params(env['PATH_INFO']))
  -    catch(:pass) { return route.call(env, app: self) }
  +    catch(:pass) { return route.call(env) }
     end
   rescue => error
     if error.respond_to? :call
  
positive.code:     end
    end
  
    def call_after_filters
      if app
        app.class.after_filters[:all].each { |filter| app.instance_exec(env, &filter) }
        after_filters.each                 { |filter| app.instance_exec(env, &filter) }
  
negative.code:     def generate_map(default_app, mapping)
        mapped = default_app ? { '/' => default_app } : {}
        mapping.each { |r, b| mapped[r] = self.class.new(default_app, &b).to_app }
        Rack::URLMap.new(mapped)
      end
    end
  end
  ```
  
  Let's add a spec (spec/builder_spec.rb) for this new Builder class:
  
  ```ruby
  describe Eldr::Builder do
  