Shared var between processes

Hi,

I'm trying to share a var between the different processes of my prefork  
Apache.

I then tried the following idea :
$r->server()->dir_config('var','val');
Unfortunately, $r->server()->dir_config('var') is not shared among the  
processes.
I would have thought config was stored at the very first Apache process  
(the parent) level.

Other solution is IPC::Shareable (one more module to load :-/)

Any other solution ?
I would have been happy with an Apache-only way to do this (like I tried  
above).

I need the var to be set only one time to a constant random value, then to  
be read by the different processes.
I then also thought about an environment variable set when Apache starts,  
and then given to Perl using "PerlSetVar var ${VAR}".
But 1. var value would be disclosed into Apache env which I want to avoid,  
2. PerlSetVar at every request is perhaps not really perfect in terms of  
performance.

Thank you very much for your help !

Ben