Thanks for the response. I understand that the calling without quotes would work.
The only issue is I can't use the user field directly. It has to be referenced through foo (i.e foo -> user -> johndoe)
My real life case is something similar to this:
... | eval foo=mvindex(split(somefield,"\n"),1)."/STATUS"
As you can see the "foo" here is dynamically generated and contains a field name as a string value (eg. "TEST00123/STATUS") that I want to evaluate.