Start with:

class C
  def self.class_callme
    internal_helper
  end

  def instance_callme
    C.internal_helper
  end

  def self.internal_helper
    puts "I'm not needed by the outside world."
  end
end

My first instinct was to make internal_helper protected:

class << self
  protected
    def internal_helper
      puts "I'm not needed by the outside world."
    end
end

However, instance_methods (such as instance_callme) can't call protected
class methods.  

Is there some other idiomatic Ruby way to, er, protect internal_helper, or
another way to call it from instance_callme?  Or do I just have to do it
through lack of documentation with :nodoc:, as Rails seems to do?

Jay Levitt