module Kernel

def instance_exec(*args, &block)
  mname = "__instance_exec_#{Thread.current.object_id.abs}_#{object_id.abs}"
  Object.class_eval{ define_method(mname, &block) }
  begin
    ret = send(mname, *args)
  ensure
    Object.class_eval{ undef_method(mname) } rescue nil
  end
  ret
end