Hello, Alan.

> My feeling is that perform-replace (or, possibly, replace-highlight) is
> the best place to put a save-match-data.

Doing this in perform-replace means adding save-match-data in all places
where replace-highlight is called, so maybe better to add it only once
in replace-highlight like Jayden proposed initially.

But then it's important to add an explanatory comment since
the need of using of save-match-data is not self-evident here.

Do you think this comment is clear enough?