Although C<is_filehandle> and its friends support Perl 5.8 and above,
smart match is only available in Perl 5.10 onwards.
+=head2 Use with Scalar::Does
+The smart match constants can also be used with L<Scalar::Does>:
+ if (does $file, FileHandle)
+ elsif (does $file, FileName)
Because there is some overlap/ambiguity between what is a filehandle