The INSTRUCTIONS section of the form includes a call to a function funcname, and sperform assumes that this is the name of an external C function. However, the name and address of each such function must appear in a static array that is named userfuncs. That array, along with the computer code of the external functions, is linked with a custom version of sperform. Because name did not appear in the array, sperform cannot call it.
Check that you are executing the correct, customized version of sperform (the original version of the program has no external functions linked to it). Check to see if funcname is correctly spelled. Then examine the source of the C functions to make sure that the userfuncs array is defined correctly.