while (my $logline = <LOG>) {
    # parse it
}

##</code><code>##

sleep 1 unless $. % 100

##</code><code>##

sub CPU_used {
   (map $_->[0]+$_->[1], [times])[0]
}

##</code><code>##

CPU_start();
while (my $logline = <LOG>) {
    # parse it
    CPU_max(.2) unless $. % $lines_per_second;
}