Well, that is kind of the entire point of the question :-) my regex answers emulate operations on integers larger than the input, because those operations can't be done directly without enough "scratch space" to work in. With scratch space, they'd be much smaller.
But I don't know enough about Trilangle to know *how* nontrivial it'd be to implement bigint multiplication in it. I do know that in Brainlove it'd be manageable.