For _*EVERY*_ circumstance in which an error may occur while running a program, ensure there is some way to programmatically check beforehand whether the error would occur - e.g. there is a way to check for 1D array index out of bounds, using LEN, but LOAD "DAT:DATFILE",DATARRAY will cause an error if DATARRAY has the wrong number of dimensions, and I cannot check this before getting the error.