The algorithm won't be hard if you can say what you're aiming for. Doesn't have to be a formal statement of requirements, an example is fine as long as it covers the obvious questions.

I'll go ahead and assume the input log is sorted by timestamp and in fixed-width format. 

# see manpage for unpack
my $TEMPLATE = 'A20 @28A9';

# read the input log into a hash
my %last_time;
while (<DATA>) {
    my ($timestamp, $id) = unpack $TEMPLATE;
    $last_time{$id} = $timestamp;
}

# print the output log 
# I have omitted the header

for my $id (sort keys %last_time) {
    print "$id\t$last_time{$id}\n";
}

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In reply to Re: Comparing Dates and Reoccurance by Narveson
in thread Comparing Dates and Reoccurance by tuakilan

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