my(%date_hash) = ();

my(@start_date) = qw(01-06-2007 01-08-2006 01-06-2006 01-07-2007 06-01-2007);

my @sorted_dates = sort({
                          ($date_has{$a} ||= &trans_date($a))
                          <=>
                          ($date_has{$b} ||= &trans_date($b))
                        } @start_date);

print join("\n", @sorted_dates);

sub trans_date
{
    my $date = shift;
    $date =~ s/(\d{2})-(\d{2})-(\d{4})/$3$2$1/;
    return $date;
}