What if the filehandle is a pipe, socket, or opened to a scalar, etc? I don't think there is anything that is simple and cross-platform Perl. But why would you need this? If you opened the filehandle with your script, you ought to know where it's coming from or going to. :-)

You can get the file descriptor for the filehandle. Read "perldoc -f fileno"

perldoc -f fileno

       fileno FILEHANDLE
               Returns the file descriptor for a filehandle, or
               undefined if the filehandle is not open.
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