Thanks everyone for your help. It was clear that installing Strawberry Perl on a network drive was the cause of the problem, as somehow cpanm was expanding T: drive to //k030/HydPrime/cnd, when it should have expanded to \\k030\HydPrime\cnd if it was going to expand anything, tho it really should have just used T:. Anyway the solution was to build on C: drive, and everything just worked! Then I copied it across to T: drive and all was good.