Hi List,
here's the version with binary trees (no changes to the spool file
format). I've added a strict_acl_vars config option (default is false),
which will let an expansion fail if an unset variable is used, so admins
can change their config (to be more safe against name typos) and then
activate it.
http://plonk.de/sw/exim/exim-4.63.named-acl-vars.patch