[exim] mask, with a list

Hi Everyone :)

I have been using the mask function successfully - however, I am having
trouble using it with a list of IP addresses...


eg

${mask:$acl_m9/24}

where acl_m9 = 1.2.3.4:5.6.7.8

Any help/advice greatly appreciated (how do I make it so that it can
handle lists? is there a work-around?).

Cheers,
Andrew.