When dealing with dates, I always convert them to YYYYMMDD, the only sane form.

for my $date (@dates) {
    my @parts = split qr!/!, $date;
    if ($parts[2] < 50) { # arbitrary cutoff
        $parts[2] += 2000
    } else {
        $parts[2] += 1900
    };
    $date = join "", @parts[2,0,1];
};

@sorted = sort @dates;
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Conversion back to the other date format is left as an exercise to the reader