1. A computer-implemented method comprising: identifying multiple modules in a virtual machine having separation of concerns, the multiple modules each having a distinct functionality portion and a common functionality portion common to the multiple modules, where the multiple modules are intermediate code representing human-readable code compiled into a form evaluable by the virtual machine; loading aspect code into memory, the aspect code providing the common functionality that crosscuts the multiple modules; and evaluating the intermediate code to execute the multiple modules to generate the distinct functionalities by evaluating the multiple modules, and to generate the common functionality of the aspect code via callback in execution of the multiple modules, including referencing the aspect code for the multiple modules as a callback that passes reference to the multiple modules for executable code of the aspect.