# File lib/confstruct/hash_with_struct_access.rb, line 112
    def lookup! key_path, fallback = nil
      val = self
      keys = key_path.split(/\./)
      keys.each do |key|
        return fallback if val.nil?
        if val.respond_to?(:has_key?) and val.has_key?(key.to_sym)
          val = val[key.to_sym]
        else
          return fallback
        end
      end
      return val
    end