I suppose that you could be running as root and writing files to an NFS mounted filesystem. If your machine doesn't have root access to the remote filesystem you will be treated as a "nobody".

You could ask an admin to have the NFS fileserver allow root on your machine to root access to the file system. (Probably not a good idea security wise and some admins will wail loudly if you ask for this.) Another option would be to run as anybody but root. If this isn't an option, you could "set uid" (see perlvar) or just write your files to a local filesystem.

-- bluto