Quoting Super Search, "Match text containing [ ... ] (separate strings with [ ... ] -- default is spaces)". Strings not words, not regexes. Separated by your choice, default is spaces. Those are the whole rules. All criteria must match.

For simple search, there is no place to specify an alternate separator. Currently, simple search matches as many terms as possible, but that feature is likely to go away. It also only matches single-letter (not single-character) terms if they are separated by whitespace in the title (so simple-searching for "b deparse" won't find the nodes that simple-searching for "b:: deparse" would). Which is a mixed blessing and so might change as well.

It would be nice if MySQL either supported "LIKE '...[^a-z]...'" or it's RLIKE wasn't a huge CPU hog. Then we could allow you to match "words" along with the other criteria. But google (and others) is great at matching words (and doesn't do anything else) so getting it working again will help.