Re^3: How to safely define a CGI program's application base directory

[choroba]

What threat are you trying to avoid? It is upon you to tell what is safe. If you know there are three possible values, you can try something like

m{^(/path1|/path2|/path3)/MyApp$}

Someone can still tweak the config to point to a wrong path (valid for a different server). You can even include other conditions into the if, not only the single match.