You don't have to write the word cookie again, just use $1 to return it from the match text of the event:
on *:text:cookie:#: if (!%f) { inc -u5 %f | .describe $chan gives $nick a $1 }
And what, pray tell, is the gain in that? It serves no purpose here.
On the contrary, it requires $1 to be evaluated first. You may as well use $matchkey
