# 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";
}