my @thresh  = ( 1000, 4000, 7000, 10000 );
my @bins;

while (<LOG>) {
    my $val = ( split )[10];
    next unless ( $val =~ /^\d+$/ );
    my $i = 0;
    while ( $i < @thresh and $val > $thresh[$i] ) {
        $i++;
    }
    $bins[$i]++;
}