Using DateTime and DateTime::Format::Duration:

#!/usr/bin/perl 
use strict;
use warnings;
use DateTime;
use DateTime::Format::Duration;


my @dt;

for (qw( 30.01.08 05.03.08 )) {

    local @_ = split /\./;

    push @dt,
      DateTime->new(
        year      => $_[2] + 2000,
        month     => $_[1],
        day       => $_[0],
        time_zone => "Europe/Paris"
      );  
}

my $dur = $dt[1]->subtract_datetime( $dt[0] );
$dur->is_negative and 
    warn $dt[1]->dmy . 'is older than ' . $dt[0]->dmy . "\n";

# Choose the pattern to feet your needs
my $dtfd = 
DateTime::Format::Duration->new( pattern => '%V weeks, %e days' );
my $formated_dtd = $dtfd->format_duration($dur);

print <<QUOTE;
Difference in weeks and days,
between @{[$dt[1]->dmy]} and @{[$dt[0]->dmy]}: $formated_dtd.
QUOTE
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Date::Simple parses date strings and creates numerically comparable objects...

# Difference in days between two dates:
$diff = date('2001-08-27') - date('1977-10-05');
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