If $filename does not have a trailing slash, this could very well be an endless loop. That fits the behavior you're seeing. My guess is that you're not passing in a trailing slash on the initial call. At the very least, use File::Spec's catdir() function to concatenate path components. While most Unix filesystems, in my experience, don't care about duplicate slashes, File::Spec will clean them for you.

At best, skip the recursion yourself and use File::Find. You could also do this with readdir instead of glob, as you're asking for everything. Beware '.' and '..' though.