On Saturday, 24 Mar 2018 at 22:24, Vikas Rawal wrote:
> I am trying to write a LaTeX export filter that should replace all
> table rows with cells having entries such as <3cid4> by
> \cmidrule{lr}{3-4}

[...]

>   (while (string-match
>           "\\(<\\([0-9]+\\)cid\\([0-9]+\\)?>[[:blank:]]*\\([^&]+\\)\\)" row)

Could it be that you need to change the last + to *?
Haven't tried it, mind you.
-- 
Eric S Fraga via Emacs 27.0.50, Org release_9.1.6-341-g3a4fd3