If your array of dates is HUGE and you don't need to sort it - only to get the minimum date, you can extract the minimum date with simple loop:

my $min;
foreach (@dates) {
    next unless /^(\d+)-(\d+)-(\d+)$/;
    $min ||= ["$3$2$1", $_];
    next unless "$3$2$1" < $min->[0];
    $min = ["$3$2$1", $_];
}
my $mindate = $min->[1];
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The idea is simple - the dates can be compared as numbers if they are written in the format YYYMMDD. The sorting can be optimized using the same technique, but you can do it yourself :)