I think you're going to have to be more specific here. What $basedir are you talking about?

In general, if you're doing some sort of recursive directory traversal, you'll want to test high up in the loop whether or not the current directory is excluded. If it is, then return immediately (which automatically excludes everything below the current directory), otherwise keep on descending.

Otherwise you can just make a list of everything below $basedir and grep out whatever you want to exclude.