Anonymous Monk, I tested  use lib '.'!

(at least I thought :)

I supposed that lib takes the file's path as base.

The perldoc wasn't clear¹, so I tested by changing the working directory with chdir before use and it seemed to work fine.

But now I am realizing that I should have put the chdir into a BEGIN block, otherwise it happens too late.

So your point is valid!!!

¹) but led me now to FindBin