"Indirect filehandles also make it easy to pass filehandles to and return filehandles from subroutines."

Okay, so how do I find out which file this filehandle references?

They way you pose the question makes me think the latter should follow from the former.

I think how easy it is to pass around filehandles is complete unrelated to finding out file names. Do note you question may not have a unique answer:

• A "file"handle may actually read or write from a socket. Or a pipe.
• The file handle may be STDIN, STDOUT or STDERR.
• Or it may be some other redirection.
• Even if the file handle accesses a real file, the file may not have a name.
• Or the file may have more than one name.