my %range_counts = ();
my %counts = ();
while( $entire_file =~ m/(\d+)bn(\d+), bytes/sg ) {
    $range_counts{'4kset'} ++ if $2 > 4000 and $2 < 6000;
    $counts{$2} ++ if $2 > 4000 and $2 < 6000;
}

print "there were $counts{'4kset'} 4000-6000 lines\n";