#!/usr/bin/perl
use warnings;
use strict;

use POSIX qw/ mktime strftime /;

# Get timestamp input from user
print 'Enter a timestamp in mm/dd/yyyy hh:mm:ss format: ';
chomp( my $stamp = <STDIN> );

my ( $month, $day, $year, $hour, $minute, $second ) = $stamp =~ m! (\d+) / (\d+) / (\d+) \s+ (\d+) : (\d+) : (\d+) !x;

# Get time value in seconds since Epoch with mktime
my $now = mktime $second, $minute, $hour, $day, $month - 1, $year - 1900;

my $realanswer = strftime '%m/%d/%Y %H:%M:%S', localtime $now + 300;

print "$stamp + 5 minutes is $realanswer\n";