I've got an idea. Let's use a single character, instead of a keyword here. (for k=1, 10 do (for j=1, 10 do (for i=1, 10 do f(i, j, k) )))
Or (for k=1, 10 do (for j=1, 10 do (for i=1, 10 do f(i, j, k)]