  In this talk I describe work on computing non-leptonic matrix elements
consistently with both long and short distance contributions included. On the
simpler example of the $\pi^+$-$\pi^0$ mass difference I explain in detail the
matching procedure and the difference between various low-energy models. I then
explain the new difficulties in non-leptonic Kaon decays and how the matching
here can in principle be done in the same way when scheme dependences are
correctly accounted for. In the end I summarize the results J. Prades and I
obtain for the $\Delta I=1/2$ rule and $B_6$.
