#!/usr/bin/perl

use strict;
use warnings;
use DB_File;

my $a = new DB_File::HASHINFO; 
my $doi = '10.1353/ham.2005.0020';

tie my %H, "DB_File", "audit.db", O_RDWR|O_CREAT, 0666, $a;
print "|$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;