We describe the implementation of ff-RPL, a shell to support structured parallel programming development in FastFlow. The shell provides ways to explore the space of functionally equivalent, alternative parallel implementations of the same application with different non functional properties. The tool is entirely written in C++ and has been designed in such a way it can be easily extended to take into account new non functional features, refactoring and optimization rules, as well as different parallel patterns. Preliminary experimental results are shown relatively to the code generation part.