You first need to get your data into an array of array refs. Assuming your date in the first elemeent:

while <FH> {
    my @$record = split $delimiter, $_;
    push(@unsorted, $record);
}
@sorted = sort { $b->[0] cmp $a->[0] } @unsorted;
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Note the order of $a, $b since you wanted oldest first, i.e., descending sort.