[Exim] config in a file?

I have configuration similar to the following:

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smtp_etrn_hosts=mail.domain1.net:server.domain2.com



etrn_router:
driver = domainlist
domains = domain1.com:domain2.org
transport = remote_smtp
route_list = "domain1.com mail.domain1.net byname;domain2.org server.domain2.com byname"

--------<>-------


I would like to put the domain and host-specific data together in one
file, and reference this file for the smtp_etrn_hosts option, and the
domain and route_list options in my router. The key is I want to have
ONE authoritative file that is used in all locations.. I'm not sure how
to go about doing this.. I could have a list of domains for 'domains',
or a list of hosts for 'smtp_etrn_hosts', and I'm sure its possible to
have route_list go in a file, but how to get all the data in one file,
and have each item extrace what it needs? (Note, Im looking for a
plain-text solution, no DBM or CDB needed)