Hrmm, while your approach would certainly work, I would hold some concerns as to the scalability of this approach under high server load. From the description of your problem you might do better to look at a caching solution which automatically encompasses this type of object expiry and clean-up - The Cache modules provide a means to perform just what you require, persistent data with a specific expiry time.

An example of usage which creates a Cache::FileCache cache in /tmp/cgi-data with a default expiry time of 15 minutes and auto-purge set (upon object retrieval) ...

use Cache::FileCache;

my $cache = Cache::FileCache->new({
    'cache_root'            =>  '/tmp/cgi-cache',
    'default_expires_in'    =>  900,
    'auto_purge_on_get'     =>  1
});
$cache->set( $key, $data );

.
.
.

$cache->get( $key );
[download]

The usage of the Cache modules is relatively straight-forward, incorporating clear and self-explanatory method names, and the provided documentation is excellent. I would strongly recommend having a look at this set of modules as this approach provides you with a pre-built method to implement data persistence with expiry without having to incorporate forking and clean-up within your script.