If you know a bit about regular expressions, you could refine your event with back references, like in (just an example)
Code:
on @*:action:*:#: {
  if ($regex($1-,/^slaps? $+(\Q,$me,\E) ?(.*)/Si)) {
    ; whatever your action for no slap item
    if (!$regml(1)) { msg $chan ouch! }
    ; whatever your action for a trout slap
    elseif (trout isin $regml(1)) { describe $chan eats the trout - yummy! }
    ; whatever your action for a different slap
    else { describe $chan slaps $nick back $regml(1) $+ ! }
  }
}