I think you need something like this: use lib "path/to/Chess path/to/Chess/Piece"; 
use lib "path/to/Chess";
use Chess::Piece::Knight;
use Chess::Piece;

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Oh, geeze this Piece directory as well as Piece.pm looks like trouble to me.

In reply to Re: How to use a .pm file in a .pl file in another directory. by Marshall
in thread How to use a .pm file in a .pl file in another directory. by tommyxd

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