code: function (singular, plural) {
      _plural(new RegExp("(" + singular.substr(0, 1) + ")" + singular.substr(1) + "$"), "$1" + plural.substr(1));
      _singular(new RegExp("(" + plural.substr(0, 1) + ")" + plural.substr(1) + "$"), "$1" + singular.substr(1));
  }
docs: Specifies a new irregular that applies to both pluralization and singularization at the same time. This can only be used
  # for strings, not regular expressions. You simply pass the irregular in singular and plural form.
  #
  # Examples:
  #   irregular 'octopus', 'octopi'
  #   irregular 'person', 'people'
  @param singular the singular version
  @param plural  the plural version