1. A method for modifying computer program instructions during execution of those instructions, the method comprising computer-implemented steps of: writing a first value into a memory location, wherein the first value represents a first instruction, and wherein the first instruction is a patch class instruction; fetching the first instruction from the memory location; executing the first instruction; and overwriting a second value into the memory location, wherein the second value represents a second instruction, and wherein the second instruction is a patch class instruction; wherein the overwriting may be concurrent with the execution of the first instruction.