Use this instead to put your path in front of what is your default @INC, change 'unshift' to 'push' if you want it to be at the end. IMHO this is easy enough that I have never used 'use lib'. Perhaps 'use lib' provides some extra hints to the compiler that this method doesn't, but I have yet to encounted any problems.
sub BEGIN { unshift @INC, qw(d:\\mydir\\mylibs); }