[exim] Filter separator

Hi all. Have a quick question but can't find the answer anywhere. I need to
change the separator in a filter expression, so that:

${filter{a,b,c}{!eq{$item}{b}}


returns "a,c"

Also, can I use a AND or OR expression here, something of the sort of:

${filter{a:b:c}{!eq{$item}{b} AND !eq{$item}{c}}


so that this returns just "a". I would try this, but doesn't see the best
way to achieve it:

${filter{${filter{a,b,c}{!eq{$item}{b}}}{!eq{$item}{c}}


FYI, I need this to filter some addresses in a custom filter, where I need
to remove two specific addresses from certain emails, so that "a,b,c" would
actually be $h_To.

Thanks for all!

Maxi Cooper
*EGS* | Gestionamos pedidos.
Tel.: 11 5917 2513 | 15 4070 6215
egsolus.com.ar