I just discovered what I consider to be a bug in parenmatch. Consider
(3  +
 4 -   1)
When I type the closing paren or put the cursor on the second line and hit ^0, the highlight extends from ( to ), inclusive, as it should. If I put the cursor on the first line and hit ^0, the highlight extends from just ( to +. I will review this next, looking for a possible fix and to make sure there is no test 'validating' the bug. It would be better to have a correst test that is skipped.