while (1) {
    my $timeout = 5 ;
    while (@events) {
      $timeout = $events[-1]->[0] - Time::HiRes::time() ;
      last if ($timeout > 0.001) ;

      my ($time, $rsub, @args) = @{pop @events} ;
      $rsub->(@args) ;
      $timeout = 5 ;
    } ;

    # use IO::Select recommended, but this is just for illustration...
      
    select(my $rout = $rin, my $wout = $win, my $eout = $ein, $timeout) ;

    # .....
  } ;

  # add_event($delay, $rsub, @args)
  #
  #   schedule call of $rsub->(@args) in $delay (float) seconds in the future

  sub add_event {
    my ($delay, $rsub, @args) = @_ ;

    my $when = $delay + Time::HiRes::time() ;

    push @events, [$when, $rsub, @args] ;

    if ((@events > 1) && ($events[-2]->[0] < $when)) {
      @events = sort { $b->[0] <=> $a->[0] } @events ;
    } ;
  } ;