with [select] you are on the right path. but you can also use [route].

[route 20] will filter lists according to their indexes correctly but it cuts the first value in incoming lists off, so that you had to regenerate it.

you basically only need to do

[route 20]
|
[prepend 20]

and you have a working filter.

note that both, [route] and [prepend] can be "set" dynamically when they only have 1 argument.

if you want the same for general purpose you have to make sure that "20" can also pass when it comes as single number and not as list. this can be done like in the picture. (which here only takes arguments and is not dynamic.)

@Roman,

You could use routepass and you wouldn’t have to muck around with prepend.

-E

Oh for sure, I was just pointing out the alternate routing object, I just found that one recently and it helped eliminate a ton of extraneous prepending :)