A method to instrument software code may comprise marking one or more blocks of code in an application program to provide a marked code. The marking may comprise inserting a marker at each of the one or more blocks according to a marking application programming interface (API). The one or more of the blocks of code marked according to the marking API may be transformed so that one or more functions are performed for the marked blocks. The one or more functions may not be part of the application program. The method may include executing the application program and performing the one or more functions for the marked blocks.