[exim] address during sender verification

I was doing a specialty router for some sender (only) verification,

and it finally occurred to me that during sender verification, it's
$local_part and $domain that are interesting, not
$sender_address_local_part and $sender_address_domain.  I probably
knew that at some time in the past, but I went on a spec hunt to find
it mentioned.  I didn't find it in the spec (or the book).  Is it
there somewhere?  (My guess is probably yes ... :-)
-- 
bill-exim@??? (WJCarpenter)    PGP 0x91865119
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