Jeff Pang wrote:
> vhA's programs are running under /path/a/cgi-bin, but actually, the programs of vhA can access vhB's directory (ie,they can open and write some files in /path/b/). vice versa, the programs of vhB can access vhA's directory.
>


It's not really a mod_perl thing but you need to read this:
http://httpd.apache.org/docs/1.3/suexec.html

Then you simply do this:


DocumentRoot /path/b
ServerName www.b
User user-b
Group group-b


....and the programs in /path/b/cgi-bin will run as user-b in group-b.

cheers
John