One important point about skipping: if the goal you skip over is not
determinate, and you later redo (backtrack) into the goal, you will not
be able to see the redos into goals that were skipped over. This is
because the debugger does not keep any information about the goals that
have been skipped over, in order to achieve much greater speed. You will,
however, be able to see any new calls that are executed in the process of
trying to redo the goal.