#! perl -slw
use strict;
use Time::HiRes qw[ time ];

mkdir 'myroot';
for my $l1 ( '00' .. '09' ) {
    mkdir "myroot/$l1";
    for my $l2 ( '00' .. '09' ) {
        mkdir "myroot/$l1/$l2";
        mkdir "myroot/$l1/$l2/$l1$l2$_" for  '000' .. '999';
        mkdir "myroot/$l1/$l2/$l1$l2$_/1" for '000' .. '999';
    }
}

my $start = time;
for( 1 .. 1000 ) {
   my $id = sprintf "%02u%02u%03u", int( rand 10 ), int( rand 10 ), int( rand 1000 );
   my( $l1, $l2 ) = unpack 'a2a2', $id;
   opendir D, "myroot/$l1/$l2/$id/";
   readdir D; readdir D; ## get rid of '.' & '..'
   my $count = readdir D;
   rename "myroot/$l1/$l2/$id/" . $count, "myroot/$l1/$l2/$id/" . ++$count
      or warn "$! : $id : $count";
   closedir D;
}
printf "2x2x7 took %f secs/lookup&increment\n", ( time() - $start ) / 1000;

system "rd /q /s myroot";

mkdir 'myroot';
for my $l1 ( '000' .. '009' ) {
    mkdir "myroot/$l1";
    for my $l2 ( '000' .. '009' ) {
        mkdir "myroot/$l1/$l2";
        mkdir "myroot/$l1/$l2/$l1$l2$_" for  '0' .. '9';
        mkdir "myroot/$l1/$l2/$l1$l2$_/1" for '0' .. '9';
    }
}

$start = time;
for( 1 .. 1000 ) {
   my $id = sprintf "%03u%03u%01u", int( rand 10 ), int( rand 10 ), int( rand 10 );
   my( $l1, $l2 ) = unpack 'a3a3', $id;
   opendir D, "myroot/$l1/$l2/$id/" or warn "$! : myroot/$l1/$l2/$id/";
   readdir D; readdir D; ## get rid of '.' & '..'
   my $count = readdir D;
   rename "myroot/$l1/$l2/$id/" . $count, "myroot/$l1/$l2/$id/" . ++$count
      or warn "$! : $id : $count";
   closedir D;
}
printf "3x3x7 took %f secs/lookup&increment\n", ( time() - $start ) / 1000;

system "rd /q /s myroot";

__END__
C:\test>1032393
2x2x7 took 0.002671 secs/lookup&increment
3x3x7 took 0.002761 secs/lookup&increment

C:\test>1032393
2x2x7 took 0.002628 secs/lookup&increment
3x3x7 took 0.003111 secs/lookup&increment