One of our projects has an ancient, inherited Makefile.PL based on ExtUtils::MakeMaker which contains the following:
WriteMakefile(
# ... Many lines omitted ...
PMLIBDIRS => [ 'lib', '$(BASEEXT)' ],
PMLIBPARENTDIRS => [ 'lib' ],
);
The PMLIBDIRS option is clearly explained in the documentation (linked above), but PMLIBPARENTDIRS is not documented that I can find. It is mentioned twice in the source code however, but not in what appears to be any functional way (i.e. in configuration and documentation).
Commenting out the PMLIBPARENTDIRS option does not have any immediately obvious negative impact when building the package.
What does this parameter do? Or is it obsolete?