webapp.rb

require 'rubygems'
require 'rack'

class Object
  def webapp
     def call(env)
       func, *attrs = env['REQUEST_PATH'].split('/').reject(&:empty?)
       [200, {}, send(func, *attrs)]
     end
    self
  end
end

Rack::Handler::Mongrel.run [].webapp, :Port => 9292

# http://localhost:9292/push/1  -> 1
# http://localhost:9292/push/2  -> 12
# http://localhost:9292/push/2  -> 123

# http://localhost:9292/to_a    -> 123

# http://localhost:9292/pop     -> 3
# http://localhost:9292/shift   -> 1