The docs of File::NFSLock are not the clearest I've ever read. However, with some background knowledge it's possible to surmise that this module can be used on local filesystems too. The problem with most file locking schemes when used on NFS is that they depend on certain operations which are atomic for local FS's actually being atomic -- but on NFS many of these operations are not atomic. So to introduce the concept by saying it works because something on NFS is atomic, it's a pretty safe assumption that that operation is atomic on local FS's as well and so the locking mechanism will also work there.