...
  $kernel->yield('keepalive', $io_wheel, $kernel);
  ....

##</code><code>##

  ...
  keepalive => sub {
    my ( $io_wheel, $kernel ) = @_[ ARG0, ARG1 ];
  ....

##</code><code>##

  keepalive => sub {
      my ( $io_wheel, $kernel ) = @_[ ARG0, KERNEL ];
      $io_wheel->put( "keepalive" );
      $kernel->delay( 'keepalive' => 10, $io_wheel );
  },