-exim -be -oMs my.target.host.name
-'\${listextract {2} {<. $sender_host_name}}' => '${listextract {2} {<. $sender_host_name}}'
+exim -d-all+expand -be
+set,t acl_m0 = my:target:string:list
+'\${listextract {2} {$acl_m0}}' => '${listextract {2} {$acl_m0}}'