This is because the code dosen't run out-of-the-box. You need to supply some "colors" (as numbers and filenames) for the quilt in the hash %numbers_to_fabrics.

An interesting project would be to add the capability to read a directory full of images and mush them into a quilt. Also interesting would maybe be to add more user/error feedback - both projects can be easily completed by using Perlmonks Super Search (search for "Reading Directory" and/or File::Find) and by looking at the program code and carefully sprinkling print statements here and there.