[exim] Help crafting a prefix-only hostname wildcard match

Folks,

First time I've had a need, so I'm sure I've overlooked the obvious..

Wanted:

A match to the first suffix *only* in a $sender_host_name or
$sender_helo_name, regardless of presence, absence, or count of
subsequent suffixes, if any, or even a proper <domain>.<tld>

As in:

<match-pattern>.<don't care1>.<don't care2>.<don't care"n">


From docs, AFAICS, the various 'wildcard' lookup or match tools;

- Either apply only to the right-end of a complex string, as in:

<don't care><.<don't care>.<match-pattern>


- OR apply to a specified 'count' or 'countdown' of chunks, effectively
walking thru positions from, again AFAICS, the right-end, not the left.

Can someone please kick me w/r what I am missing?

;-)

Thanks,

Bill Hacker