Optional catch-all — segment [[...region]] = []
Indo-Pacific range
The Nicobar Pigeon roams across thousands of small islands. The path /habitat/[...region] walks an arbitrary depth of the geography to demonstrate catch-all segments.
Drill in
On the next outbound RSC fetch, this optional catch-all encodes as ["region", "", "oc"] when populated, or just disappears from the path when empty. The "oc" type distinguishes it from a required catch-all [...region] (which would be "c").