in reply to Which takes priority site\lib or lib?
It is a common and stupid bug with dual-lived modules , if you look around, I'll bet you'll find more
2006 Bug #25163 for Test-Simple: Set INSTALLDIRS = perl for 5.6.2
2010 Bug #57201 for CPANPLUS: installdirs should be site when > perl 5.11
If you're sticking with perl $] >= 5.009005 && $] <= 5.011000 you can isolate yourself from these Makefile.PL oversights with
perl Makefile.PL INSTALLDIRS=perl
or, even though no core modules use it, perl Build.PL installdirs=core