Why CPAN behaves this way, and whether it should be considered a bug or a feature, is still open I suppose.

Well, CPAN is used to update your system installation, so it seems pretty sensible to me for it to remove '.' from the search path. It doesn't want modules from just somewhere (and "." is somewhere) for modules to satisfy their dependencies, but only from perl's libdirs.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}