ZIS flow working with multiple variables in a transform action

Hey all,

I've build a flow to update the phone identities of a user if specific custom fields have been changed.

What I did so far is, that I get the previous custom field value (e.g. +49 030123), it is the value of the variable: $.input.user_event.previous and with that I call the identities endpoint and find out the identityID to make an update with the current value ($.input.user_event.current).

That works very well so far with these expression:

"expr": '.identities[] | select(.value == "+49 030123") | .id | tostring',

Now I would like to use not the hardcoded number, rather the variable itself -> $.input.user_event.previous and my code looks like this:

"find_phone": {
          "Type": "Action",
          "ActionName": "zis:common:transform:Jq",
          "Parameters": {
            "data.$": "$.identities",
            "expr": '.identities[] | select(.value == "{{$.input.user_event.previous}}") | .id | tostring',
          },
          "ResultPath": "$.identity",
          "Next": "Ok"
        },

But it doesn't work, it seems that the previous variable is blank. It works only with a hardcoded value. So it seems that it is not possible to access to the input variable because the expression is within the data parameter $.identity (which is the API output of all identities of an user).

I am totally confused because if I use just a message to log it, works. My code looks like this: