I searched for payload in the docs and didn't find it

[danr]

The document talks about payloads at some places. They seem to be the ruby/rust-esque pipe-delimited blocks but it is never really defined.

[nektro]

"payload" is the result of a "capture". you can see it in more detail here https://ziglang.org/documentation/master/#Keyword-Reference in the docs for if, while, switch, for, catch.