From Perl Cookbook:

($seconds, $minutes, $hours, $day_of_month, $month, $year, $wday, $yda
+y, $isdst) = localtime($time);
printf("Dateline: %02d:%02d:%02d-%04d/%02d/%02d\n", $hours, $minutes, 
+$seconds, $year+1900, $month+1, $day_of_month);
[download]

If you don't feel like doing the formatting yourself, there are also... many... date/time-related modules on CPAN.