C:\>perl -le "print \"@INC\""
C:/MinGW/perl516/site/lib C:/MinGW/perl516/lib .

C:\>set PERL5LIB=C:/rubbish

C:\>perl -le "print \"@INC\""
C:/rubbish C:/MinGW/perl516/site/lib C:/MinGW/perl516/lib .

C:\>