mixins In Perl6

mixins.pl6

# mixins are called roles in perl 6 and also can behave as traits and interfaces
class ALogger { method debug( Str:D $message ) {...}}

class BLogger { method debug( Str:D $message ) {...}}

role Logger {
   method log( Str:D $message ) { ... }
}
role LoggerInfo {
   has $!log = ALogger.new();
}
role LoggerDebug {
   has $!log = BLogger.new();
}

class MyLogger does Logger, LoggerDebug, LoggerInfo {
    method log( Str:D $message ) {
         $!log.debug($message);
     }
}

class Handler { # Logger and UberLogger are valid
        method logHelloWorld( Logger:D $log ) {
                $log.log("hello world");
                # could call error, can't call trace (or maybe you can but shouldn't)
        }
}