Where is OCaml's alternative string syntax {|...|} documented?

Question

OCaml's syntax for string literals

let s = "..."

is explained in the manual at the expected position:

However, OCaml has an alternative syntax for string literals which is especially handy for regular expressions and multi-line strings:

let s = {|...|}
let s = {foo|...|foo}

Where is that documented?

vog_19163 · Answer

To answer this question myself, the syntax was originally described in the extensions chapter of the OCaml manual:

Thanks to glennsl and octachron for pointing this out.

Update: Meanwhile it has been moved to the expected, more visible, places: