app.rb

class MyApp
  def call(env)
    [200, {'Content-Type' => 'text/html'}, ['<a style="background-color:red;">URGENT MSG</a> from Tiny Tim: Hello']]
  end
end

config.ru

require './app.rb'
 
class ContentType
  def initialize(app)
    @app = app
  end
 
  def call(env)
    status, headers, body = @app.call(env)
    headers["Content-Type"] = "text/html"
    [status, headers, body]
  end
end
 
class FinishSentence
  def initialize(app)
    @app = app
  end
 
  def call(env)
    status, headers, response = @app.call(env)
    
    response_body = ""
    response.each {|part| response_body += part}
    response_body += " World!"
 
    headers["Content-Length"] = response_body.length.to_s
 
    [status, headers, [response_body]]
  end
end
 
 
use FinishSentence
use ContentType
run MyApp.new