[<channel>] <stat expression>
Returns the ranking of users according to the given stat expression.
Valid variables in the stat expression include 'msgs', 'chars',
'words', 'smileys', 'frowns', 'actions', 'joins', 'parts', 'quits',
'kicks', 'kicked', 'topics', and 'modes'. Any simple mathematical
expression involving those variables is permitted.