How to do this Idiom in Rails 3

gistfile1.rb

#!/usr/bin/env ruby                                                                                                                                                                                                                                                          

# works in rails 3 

RAILS_ENV = ARGV[0]

if RAILS_ENV.nil?
  puts "usage: blah.rb environment"
  exit
end

ENV['RAILS_ENV'] = RAILS_ENV

require File.expand_path(File.join(File.dirname(__FILE__), '..', 'config', 'application'))

puts Rails.env

# Do something smart here