Example using modules within modules to create private namespaces

ruby.rb

module MyFirstModule
  def first_public_method(my_string)
    return "#{my_string} #{PrivateMethods.private_method}"
  end

  module PrivateMethods
    def self.private_method
      1
    end
  end
end

module MySecondModule
  def second_public_method(my_string)
    return "#{my_string} #{PrivateMethods.private_method}"
  end

  module PrivateMethods
    def self.private_method
      2
    end
  end
end

class MyClass
  include MyFirstModule
  include MySecondModule
end

puts MyClass.new.first_public_method("hey") # => "hey 1"
puts MyClass.new.second_public_method("hey") # => "hey 2"