I am worried about how the PERL5 LIB env variable affects different perl installations. I am presuming they share the same one. However I want to be sure that if I set the PERL5LIB for my local installation that it won't mess up the system installation. I want to include certain module versions for use by my local installation and I know if i set PERL5LIB it is prepended to the @INC array. Presumably this will affect my system installation too. I don't know if I can avoid this or whether it means I shouldn't use the PERL5LIB variable and I should use 'use lib' to modify the INC array.