[exim] Any limitations in exims expressions?

Hi

i'm trying to build a (i think very long) "server_condition" expression
for the plaintext authenticator (on server-side).

The authenticator consists of 2 long expressions. For itselfs, each one
works fine. But when i combine them to one big expression, i'll get some
expression errors. I'm very sure, that the expression is correct, so i
belive, that the expression is to long ( ~30 brackets ) for exim.

Any suggestions, where the problem is?
Thanx
Mirko