We introduce the notion of a perfect process tree as a model for the full propagation of in forma tion in metacomputation. Starting with constant propagation we construct step-by-step the driving mechanism used in supercompilation which ensures the perfect propagation of information. The concept of a simple supercompiler based on perfect driving coupled with a simple folding strategy is explained. As an example we demonstrate that specializing a naive pattern matcher with respect to a fixed pattern obtains the efficiency of a matcher generated by the Knuth, Morris & Pratt al gorithm.