Not too sure of the 'fun' part
but it was enlightening. In reality, I had not notion of xpath, other than the small area in calibre when converting books. But I reviewed the expressions in the pre-defined webpages and to see what was matched to determine why. With alot of trial and error I got one to work and just kept plugging from there.
The highlighting was invaluable in seeing exactly what was matched.
I realized the test library was not needed if 'finish' was not selected, but desired to see the results in calibre.
If there is no simple way to enter an expression in the plugin entries a popup dialog would be good.
In the meantime, the edit bulk metadata will remove the parenthesis and pound sign.