cog While I agree that a Schwartzian transfrom is a good idea here, I would like to make two small comments.

1. Rather than doing three comparisons, first on year, then month, then day, I believe (though I haven't benchmarked it) that it would be faster to do a single comaprison of a string in the form yyyymmdd, which can be easily created with a regex.

2. Depending on your data set, it maybe considerable faster to use an Orcish manouver. Especially if the same date may appear multiple time in the list (and I didn't nessicarily see anthing in the post to indicate that that wouldn't happen).

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;
}
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