use strict;
use warnings;

my $time_left = 1*60*60; # in secs.

while ($countdown--) {
   printf("\r%02d:%02d:%02d",
      $time_left / (60*60),
      $time_left / (   60) % 60,
      $time_left           % 60,
   );

   sleep(1);
}

print("\rKABOOM!!!!\n");