use Tk;

my $mw = MainWindow->new();

my $level = 0;

my $id = $mw->after (1, \&_after);

sub _after
{
    if ( $level < 5 )
    {
        $level++;
        my $id = $mw->after (1, \&amp;_after);
    }
    else
    {
        $level--;
    }

    print "$level";
}


MainLoop;

1;