Thank you, you're right. I've tested the old and revised code, and the double backslash wasn't neccesary.

I've attached the revised patch.

On Tue, 25 May 2021, at 11:00, Basil L. Contovounesios wrote:
> "Colin Woodbury" <colin@fosskers.ca <mailto:colin%40fosskers.ca>> writes:
> 
> > +    (let* ((patt "[ \\t\\n\\r.]+") ; Borrowed from `string-trim'.
> 
> Those backslashes need escaping only in string-trim's docstring, not in
> the literal regexp string.
> 
> Thanks,
> 
> -- 
> Basil
>