set_permission (Irc::Bot::Auth::PermissionSet)

    # 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