# File lib/rbot/botuser.rb, line 160
      def set_permission(str, val)
        cmd = str.to_irc_auth_command
        case val
        when true, false
          @perm[cmd.command] = val
        when nil
          @perm.delete(cmd.command)
        else
          raise TypeError, "#{val.inspect} must be true or false" unless [true,false].include?(val)
        end
      end