How to add to search based on the token being set

[amdosh]

I want to add a few rex statements to my existing search based on the token being set. Please see example below. 

ex:
| regex _raw="$token1$"
if($token2$){
| regex _raw!="abc"
| regex _raw!="xyz"
}

Please let me know if I can achieve this in some other way. Thanks!