This is how I would maybe work around the problem of scoping monkey patches. Which should be coming in Ruby 2.0

scoped-monkey-patch.rb

module Test
  class String < ::String; end
  
  p String.new("Test::String").class
  #=> Test::String
  p ::String.new("::String").class
  #=> String
  p "::String".class
  #=> String -> Would be better as Test::String
end

p Test::String.new("Test::String").class
#=> Test::String
p String.new("::String").class
#=> String
p "::String".class
#=> String