use strict;
use warnings;
use Date::Calc qw(Mktime); # Turns a date string into seconds since epoch

my $dt_str2="31/12/2009 6:29:26 p.m.";
my $dt_str1="31/12/2009 6:14:25 p.m.";

my ($day, $mo, $yr, $hr, $min, $sec, $mer) = 
   $dt_str1 =~ m{(\d+)/(\d+)/(\d+) (\d+):(\d+):(\d+) ([ap])};
$hr += 12 if $mer eq 'p';
die "Problem with date string $_" if $hr > 23;
          # Note element order for Date::Calc functions!
my $dt1 = Mktime($yr, $mo, $day, $hr, $min, $sec);

($day, $mo, $yr, $hr, $min, $sec, $mer) = 
   $dt_str2 =~ m{(\d+)/(\d+)/(\d+) (\d+):(\d+):(\d+) ([ap])};
$hr += 12 if $mer eq 'p';
die "Problem with date string $_" if $hr > 23;
my $dt2 = Mktime($yr, $mo, $day, $hr, $min, $sec);

print $dt2 - $dt1, "\n";

##</code><code>##

use strict;
use warnings;
use Date::Calc qw(Mktime); # Turns a date string into seconds since epoch

my $dt_str2="31/12/2009 6:29:26 p.m.";
my $dt_str1="31/12/2009 6:14:25 p.m.";

my @dates_to_compare;
for ($dt_str1, $dt_str2) {
    my ($day, $mo, $yr, $hr, $min, $sec, $mer) = 
       m{(\d+)/(\d+)/(\d+) (\d+):(\d+):(\d+) ([ap])};
    $hr += 12 if $mer eq 'p';
    die "Problem with date string $_" if $hr > 23;
                            # Note element order for Date::Calc functions!
    push @dates_to_compare, Mktime($yr, $mo, $day, $hr, $min, $sec);
}
# using pop clears out the array, which is helpful when looping
print pop(@dates_to_compare) - pop(@dates_to_compare), "\n";