use List::Utils qw(reduce);

my %hits = map {
    $_ => [0],
} (qw(google msn spam));

my $start = time;
my $max_queue_size = 60; # our window is 60 seconds
while (defined my $line = <$log>) {
    # process log
    my $who = get_hit($line);
    if ($who) {
        my $now = time;
        my $bucket = $max_queue_size - $now-$start;

        # Keep our queue at the appropriate length
        my $queue_length = @{ $hits{ $who }};
        if ($queue_length > $max_queue_size) {
            splice @{ $hits{ $who }}, 0, $queue_length - $max_queue_size;
        };
        $hits{ $who }->[$bucket]++; # count a hit
    };

    # Aggregate the buckets using reduce()
    # respectively update the aggregates by adding the first item
    # and subtracting the item that just fell out of the reporting window
};