Several changes:

1. Thanks, and your two suggestions were implemented.
2. In the old version, it waits even after failed to load the image; in this new version, it no longer waits in this situation.
3. The time dealyed is now a constant, for better coding style.

use Tk;
use Tk::JPEG;
use File::Glob ':glob';

use constant DELAY => 1000;

my @jpgs = bsd_glob("*.jpg");
my $index = 0;

my $mw = MainWindow->new(title => "JPEG");
my $image = $mw->Photo();
$mw->Button(-image => $image)->pack();

$mw->after(DELAY, \&next_image);
MainLoop;

sub next_image {
    $image->blank();
    if (eval {$image->read($jpgs[$index]); 1}) {
        $mw->configure(-title => $jpgs[$index]);
        $mw->after(DELAY, \&next_image) if (++$index <= $#jpgs);
    } else {
        $mw->after(0, \&next_image) if (++$index <= $#jpgs);
    }
}
[download]