This is really something that's not easily made platform independent. If you can limit yourself to a single OS you might can find some pattern to the dev_t numbers (negative for NFS apparently doesn't hold on your platform). One way which only depends on a single external command would be:

• parse the output from df to build a list of filesystems and their type
• for each filesystem save off the dev_t value from (stat( "$mountpoint/." ))[0]
• compare (stat( $file_in_question ))[0] to your saved dev_t list

More of a long shot would be to use Inline::C to get a version of the major()/minor() macros (or hand-roll them), and then compare those against disk device files in /dev. If there's one with the same major/minor, it's a local file; if not it's probably remote (but then you probably wouldn't be able to figure out NFS vs SMB vs . . .).