EXHOST regular expression syntax

[Anna Jonna Armannsdottir <annaj (at) hi.is>]

In my University, all hosts on a page run a dsmc process. 
However, there are exceptions from the rule. 
In the hobbit-clients.cfg file, 
The rule that used to work is like this: 
PROC	dsmc EXHOST=%.jotunn.rhi.hi.is

Now, yet another host is also exempt from the rule, so 
I tested the following rules:
PROC	dsmc EXHOST=%.jotunn.rhi.hi.is EXHOST=bestla.rhi.hi.is
PROC	dsmc EXHOST=%.jotunn.rhi.hi.is,bestla.rhi.hi.is

Both rules give unexpected results. So I expect that the rule 
should be written as a single regular expression, but I 
do not know the syntax. Can anybody refer me to a description 
of the syntax. 

-- 
Kindest Regards, Anna Jonna Ármannsdóttir,       %&   A: Because people read from top to bottom.
Unix System Aministration, Computing Services,   %&   Q: Why is top posting bad?
University of Iceland.