1. A method for modifying a computer program, the method comprising: replacing a number of original code segments in the computer program with a number of virtual types that receive new values for current values from instruction strings that interact with the number of virtual types during execution of the computer program; utilizing a header file associated with the computer program to define a number of values that correspond to the number of virtual types; receiving an instruction string that includes a command line switch, a new value for a virtual type, and instructions to replace a current value in the virtual type with the new value; and utilizing the header file to replace, responsive to the instructions, the current value in the virtual type with the new value, wherein the new value modifies the computer program, and wherein the computer program is modified while the computer program is executed by a processor unit.