vendors are those who build and distribute perl binaries, (ActiveState/Strawberry Perl/Redhat)...

modules which vendors add to the standard perl distribution get installed into vendor directories (sometimes vendors reuse site directories).

Modules you (or your admin) install go into site directories.

Modules installed in privlib are those which come with perl (core modules).

$ perl -V:install.*
installarchlib='D:\strawberry\perl\lib';
installbin='D:\strawberry\perl\bin';
installhtml1dir='';
installhtml3dir='';
installhtmldir='';
installhtmlhelpdir='';
installman1dir='';
installman3dir='';
installprefix='D:\strawberry\perl';
installprefixexp='D:\strawberry\perl';
installprivlib='D:\strawberry\perl\lib';
installscript='D:\strawberry\perl\bin';
installsitearch='D:\strawberry\perl\site\lib';
installsitebin='D:\strawberry\perl\site\bin';
installsitehtml1dir='';
installsitehtml3dir='';
installsitelib='D:\strawberry\perl\site\lib';
installsiteman1dir='';
installsiteman3dir='';
installsitescript='D:\strawberry\perl\site\bin';
installstyle='lib';
installusrbinperl='undef';
installvendorarch='D:\strawberry\perl\vendor\lib';
installvendorbin='D:\strawberry\perl\bin';
installvendorhtml1dir='';
installvendorhtml3dir='';
installvendorlib='D:\strawberry\perl\vendor\lib';
installvendorman1dir='';
installvendorman3dir='';
installvendorscript='D:\strawberry\perl\bin';
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