We were using memoize::expire to do some simple dns caching. I was using the example from the perldoc to setup persistant disk caching (code below)

# Code from the perldoc
use Memoize;
use Memoize::Expire;
use DB_File;

# Set up persistence
tie my %disk_cache => 'DB_File', $filename, O_CREAT|O_RDWR, 0666];

# Set up expiration policy, supplying persistent hash as a target
tie my %cache => 'Memoize::Expire',
                 LIFETIME => $lifetime,    # In seconds
                 NUM_USES => $n_uses,
                 HASH => \%disk_cache;

# Set up memoization, supplying expiring persistent hash for cache
memoize 'function', SCALAR_CACHE => [ HASH => \%cache ];
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However, the TIEHASH routine in Memoize::Expire doesn't ever appear to do anything with the HASH argument. added this code near the bottom of TIEHASH in Memoize::Expire and this seemed to work

  
if(exists($args{HASH}))
  {
      $args{C} = $args{HASH};
  }
  else
  {
      $args{C} = \%cache;
  }
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I don't know if I was missing something in the docs but the above code seems to have fixed the problem.