gistfile1.rb

module Rack
  class Request
    def subdomains(tld_len=1) # we set tld_len to 1, use 2 for co.uk or similar
      # cache the result so we only compute it once.
      @env['rack.env.subdomains'] ||= lambda {
        # check if the current host is an IP address, if so return an empty array
        return [] if (host.nil? ||
/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/.match(host))
        host.split('.')[0...(1 - tld_len - 2)] # pull everything except the TLD
      }.call
    end
  end
end
 
get '/' do
  @request.subdomains.join("<br/>")
end

class LeonIMeanNoelMiddleware
  def initialize(app)
    @app = app
  end?
  def call(env)
    status, headers, response = @app.call(env)
    new_response = response.map do |part|
      part.gsub(/Leon/, 'Noel')
    end
    [status, headers, new_response]
  end
end