  Most past work on weak nonleptonic decays has mixed dimensional
regularization in the weak operator product expansion with some form of a
cutoff regularization in the evaluation of the matrix elements. Even with the
usual technique of matching the two schemes, this combination misses physics at
short distance which can be described by dimension eight (and higher dimension)
operators. I describe some recent work with V. Cirigliano and E. Golowich which
clarifies these effects and provides a numerical estimate suggesting that they
are important.
