#!/usr/bin/env perl
use strict;
use warnings;
use Time::Piece;
use Time::Seconds;

my @durations = (qw/00:05:21 00:08:05 00:10:33/);

my $start = localtime;

for my $d (@durations) {
    print "$start plus $d = ";
    my ($hh, $mm, $ss) = split /:/, $d;
    my $t = $start + $hh * ONE_HOUR + $mm * ONE_MINUTE + $ss;
    print "$t\n";
}