Hi Abigail and hello other monks Abigail said: "I find this remark curious as the floyd_warshall sub can take a reference to a hash of hashes as argument." as a response to my remark: "I want to build a matrix using a hash of hashes so that I can delete items easily afterwards without the matrix getting illformed." Exactly! And that's why I wanted to use the floyd_warshall sub so much!! The alternatives don't give me that freedom. The problem was just getting the number of paths. I am going to take a look at the re: that followed now. -Choco