current is not valid in the script. You can also drag and drop the data pill into the acript and then dot walk to your field.

I think normally there should be an example in the script field i you open it the first time.

https://docs.servicenow.com/bundle/newyork-servicenow-platform/page/administer/flow-designer/concept/inline-scripts.html

This was my flow script: 

have you tried to use script as below

var openFor = current.opened_by.toString(); //check for the field name as well

This does not seem to work