whack

whack v.  According to arch-hacker James Gosling, to
   "...modify a program with no idea whatsoever how it works." (See
   {whacker}.)  It is actually possible to do this in nontrivial
   circumstances if the change is small and well-defined and you are
   very good at {glark}ing things from context.  As a trivial
   example, it is relatively easy to change all `stderr' writes
   to `stdout' writes in a piece of C filter code which remains
   otherwise mysterious.