1. A method for optimizing program code in dynamically-typed languages, comprising: gathering hot-type information from a program by employing at least one of inferencing and profiling to get the hot-type information for operator uses; inserting guards in the program based on data flow in the program to guard against propagation failures during runtime where preconditions are violated or where the propagation is unlikely to return; versioning the program in its entirety into global versions including a hot path version and a cold path version, where the hot path version is expected to be executed if the values of variables in the program code are expected types, and other exceptional cases are handled by the cold path version as triggered by the guards; performing compiler optimizations to remove redundant representations of values, and heavy overloading of operators to provide an optimized compiling of the program code; and combining untagging and unboxing techniques to obtain optimal representations, if needed.