$end_time = shift || "16:54:28";
$start_time = shift || "16:54:23";

if (($end_time =~ /(\d+)/)[0] < ($start_time =~ /(\d+)/)[0]
   || ($end_time =~ /(\d+)/)[0] == ($start_time =~ /(\d+)/)[0]
   && (($end_time =~ /(\d+)/g)[1] < ($start_time =~ /(\d+)/g)[1]
      || ($end_time =~ /(\d+)/g)[1] == ($start_time =~ /(\d+)/g)[1]
      && ($end_time =~ /(\d+)/g)[2] < ($start_time =~ /(\d+)/g)[2])) {
   $end_time =~ s/(\d+)/24+$1/e;
}

use List::Util "sum";
$mindiff = sum(map( 60**(2-$_)*(($end_time =~ /(\d+)/g)[$_]-($start_time =~ /(\d+)/g)[$_]), 0..2 ))/60;

print $mindiff, "minutes (", $mindiff*60, " seconds)\n";