[exim] Express list in reduce?

Hello,

    If I’ve defined a domain list thus:

domainlist mydomains = foo.com : bar.com

… is there any way to pass that domain list to, e.g, ${reduce}?

    For testing purposes I’d like to do something like:

-----
${reduce {+mydomains}{}{${if eq{$value}{}{}{$value,}}$item}}
-----

… and have it give me “mydomains”, joined with a comma.

    Alternatively, is it possible to express a filter/grep of such a list?

    Thank you in advance!

cheers,
-Felipe Gasper