Comment 3 for bug 888280

Tested one more:
+banmsgre 10 <%W%W%W%W%W> some reason
<Hub> Messages that match "%w%w%w%w%w" will be blocked (Level: 10) (Reason: some reason) (Expires: never) (Bans for 10 minutes)

+banmsgre 10 <%W%W%W%W%W> some reason 0
<Hub> Messages that match "%W%W%W%W%W" are not being blocked

+banmsgre 10 <%w%w%w%w%w> some reason 0
<Hub> Messages that match "%w%w%w%w%w" won't be blocked anymore

So, upper case set-complement, as shown in http://www.wowpedia.org/Pattern_matching, also does not work.