1. A method for modifying a computer program, the method comprising the steps of: a computer receiving an instruction string, the instruction string having new function data therein for replacing current function data of a function of the computer program during execution of the computer program by a processor unit, wherein the function is capable of being changed during execution of the computer program to modify behavior of the computer program; and the computer replacing the current function data with the new function data, wherein the new function data modifies the computer program, and wherein the computer program is modified while the computer program is executed by the processor unit.