use strict;
use warnings;
use feature qw( say );

use DateTime                   qw( );
use DateTime::Format::Strptime qw( );

my $format = DateTime::Format::Strptime->new(
   pattern   => '%d-%m-%Y',
   time_zone => 'local',
   on_error  => 'croak',
);

my $target = $format->parse_datetime('05-08-2012');
my $today = DateTime->today( time_zone => 'local' );

say $today->delta_days($target)->in_units('days');  # 123