All versions that I have available understand "/" for a directory separator, and that includes an archaic version of ActiveState.

Not all versions that I can find on machines around here have File::Spec installed. (Exceptions, an old machine with 5.004_04, and the aforementioned archaic version of ActiveState.)

Therefore for me constructing the filename with "/" is more portable than using File::Spec and catfile. However I only tested on Windows NT, Linux, and Solaris.