restful_authentication
In the case of two setting files for new user account varidation,
1, vendor/plugin/restful_authentication/lib/authentication.rb
self.login_regex = /\A\w[\w\.\-_]+\z@/ # ASCII, strict
2, lib/restful_authentication/authentication.rb
self.login_regex = /\A\w[\w\.\-_]+\z/ # ASCII, strict
then ruby prefers sometimes setting 1 and sometimes setting 2.
It seems depends on the environment.