where

for x in xs where cond do
for _, { x, y } in points where x > 0 do
if local x = f() where cond then
while local job = queue:pop() where job.ready do
case n where n > 5 then

A filter on a loop or a conditional binding, and the guard of a match arm. In a loop it emits if not (cond) then continue end on the do line, and the condition sees the loop's names, destructured ones included; on if local and while local the binding holds only when the condition does. Bindings chain with ;, if local p = a; local c = p.Character then, each seen by the next. Each binding of a chain can take its own where, if const a = x where a is Frame; const b = a.B then, and the next binding runs only when it holds; the where of the last binding filters the whole condition. if not local x = f() then return end is the guard form, with x in scope after it.