I'm not trying to save speed -- in fact, my benchmarking actually shows that what I'm trying to do is currently slower than just making the additional stat() calls.

Yes, we have bigger issues than how hard my perl code is hitting the disk, but when those bigger issues consist of already problematic data throughput off our fileservers and around the network, my perl code does have a measurable negative impact (heck... the sys-admins don't even like us doing a simple du on the filesystem in question), particularly since it's intended to be used as a fundamental module in my department.