use strict;
use warnings;

my @times = (
    '13:45:23',
    '14:12:43',
);

my $d = 0; # day
my $h = 0; # hour
my $m = 0; # min
my $s = 0; # sec

foreach my $time (@times) {
   my ($hour, $min, $sec) = split /:/, $time;
   $s += $hour * 3600 + $min * 60 + $sec;
}

$s >= 86400 and $d = sprintf('%i',$s / 86400) and $s = $s % 86400;
$s >= 3600  and $h = sprintf('%i',$s / 3600)  and $s = $s % 3600;
$s >= 60    and $m = sprintf('%i',$s / 60)    and $s = $s % 60;

print "${d}d ${h}h ${m}m ${s}s\n";