I'm *NEARLY* certain the answer is "no". Words (and only some of those - it'll barf on, if I'm not mis-remembering, 4 chars or less, complaining that the search string isn't long enough) only. No wildcarding, globbing, or regex functionality of any kind that I've been able to figure out. Unless there's some way I haven't found to tell the search "use this as a glob/wildcard/regex instead of as a word". Nothing I've tried other than keywords or UserIDs has ever given me anything but "no can do" type responses.
Not REALLY surprising, since forum software is nearly universal in assuming that every user is "too dumb" to even know what basic wildcarding (The old "*" and "?" standbys from all the way back in the days of DOS) is, let alone thinking the user capable of constructing a regex or even a half-proper glob.