how to lazyily copy a class from another module.rb

require 'rubygems'
require 'active_record'

module A
  class B < ActiveRecord::Base
    def self.a
      self.name + ' -- ' + self.object_id.to_s
     end
  end
end 

mods = ["T", "S", "R"]

mods.each do |mod|
   _mod = Module.new do
    A.constants.each do |con|
      const_set(con, ("A::" + con).constantize.dup)
    end
  end
  Kernel.eval "#{mod} = _mod"
end

puts A::B.a # A::B
puts T::B.a # T::B
puts S::B.a # S::B
puts R::B.a # R::B