submodule.rb

module Submodule
  def subset(&pred)
    mod = self

    Module.new do
      include mod

      public_instance_methods.each do |method_name|
        method = instance_method(method_name)
        undef_method method_name unless pred.call(method)
      end
    end
  end
end

Module.__send__(:include, Submodule)

p Kernel.instance_methods
p Kernel.subset { |method| method.name =~ /^define_singleton_/ }.instance_methods