PHP suEXEC is enale on my server.
But users can link to outside him directory with "ln" and seee other sites configuration files.
And its a big security issue.
Everything follow Linux/Unix file system permission, there is no magic.
Maybe, you should prevent user from execute "ln" from PHP by tighten the grip on php.ini .
There is no way to prevent the perl script from creating a symbolic link, unless you disable perl.
The best can be done is to block access to target file pointed to the symbolic link, above configuration changes does that.