Inspired by the Forum thread https://forums.gentoo.org/viewtopic-p-8578140.html#8578140.
Development of this package is continued by the author RMBARKER under the name "File-Rename". https://metacpan.org/pod/distribution/File-Rename/rename.PL
RMBARKER says that the old rename has bugs: "The original rename did not check for the existence of target filenames, so had to be used with care." (at the end of the metacpan page that I linked above)
The homepage indicated on "Gentoo Packages" is 404.
There is an ebuild for File-Rename (not the last version) in src_prepare-overlay.