anchor.diff:      
       if (!handlers.keys.contains(cmd)) {
         usage();
  -      return;
  -    }
  -    
  -    handlers[cmd](cargs);
  +      return null;
  +    }
  +    
  +    return handlers[cmd](cargs);
     }
   
     /**
  
positive.code: part of polymorphic.api;
  
  typedef void SubCommandHandler(List<String> args);
  
  /**
   * A Command Event.
  
negative.code:   /**
     * Handle Sub Commands
     */
    subcommands(Map<String, SubCommandHandler> handlers, {List<String> args}) {
      if (args == null) {
        args = this.args;
      }
      
      if (args.isEmpty) {
        usage();
        return null;
      }
      
      var cmd = args[0];
  