I was sorta guessing ... but now I looked into the code:
For VMS, W32, Mac and OS2 '$volume' means something like drive e.g. 'C:'
as for Unix its not implemented at all and always returns ''
Yes, in the filename it's not, but in the file there is (otherwise the question would be meaningless). Therefore it should be part of File::Spec.
Please observe that the module isn't called FileName::Spec or
File::Name.