@tbsp The way it works behind the scene is interpreting a single { as a JSI looking for a closing label called "lambdaXX". You can use runes with it like any other label, it's dynamically looking for its closing bracket. So you could do ={ }, -{ }, !{ }, etc..
C: https://git.sr.ht/~rabbits/uxn/tree/main/item/src/uxnasm.c#L195
tal: https://git.sr.ht/~rabbits/drifblim/tree/main/item/src/drifblim.tal#L305