I have a hash of about 40M keys and undef'd values. It has outgrown RAM, so I've tied it to a file. Now, I'm finding some keys with each that don't match with exists. How can that be?! 

use strict;
use warnings;
use DB_File;

tie (my %H, "DB_File", "audit.db", O_RDWR|O_CREAT, 0666) or die $!;
my $doi = '10.1353/ham.2005.0020';

print "|$doi| does ", (exists $H{$doi} ? "exist!\n" : "not exist!\n");

while(my $k = each %H) {
   if ($k eq $doi) {
      print "|$k| eq |$doi|\n";
      last;  # spare me the other millions...
   }
}

untie %H;

[download]

Output: 

|10.1353/ham.2005.0020| does not exist!
|10.1353/ham.2005.0020| eq |10.1353/ham.2005.0020|

[download]

Update: I should mention, this is Perl 5.8.3 and DB_File 1.808.

Update: I changed my loop to the following, and killed it after 30 minutes with over 9M keys not existing. 

while(my $k = each %H) {
   print "$k does not exist\n"  if (!exists $H{$k});
}

[download]

Update: Fixed with DB_File 1.82!

In reply to with tied hash, 'each' gives key that doesn't 'exists' by hbm

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