| This topic comes up from time to time... My take on this is that
read-only
| arrays or strings are not badly needed.

Of course, this is a matter of opinion. In the end you didn't offer
a solution to the specific problem I had. I'll still need to adopt
an expensive and/or ugly workaround if I really want to protect myself
against OCaml's mutable strings. However, I accept that my application
is not typical.

John.