There's a lot of language for such a little time, but if you have programmed any Forth it should be easy to pick up, have a look at some of the top level examples.

I have programmed about 3 Forth implementations by hand throughout the years for fun, but I have never been able to really program in it, because the stack wrangling confuses me enormously.

So for me anything vaguely complex is unreadable , but apparently not for the LLMs, which I find surprising. When I have interrogated them they say they like the lack of syntax more than the stack ops hamper them, but it might be just an hallucinated impression.

When they write Cairn I sometimes see stack related error messages scroll by, but they always correct them quickly before they stop.