I know this is an old post, but I found it today when I was trying to do something similar.
My situation was slightly different. I have a lookup file that lists the report fields and also the order they needed to be.
Here is a run anywhere example illustrating how I solved this problem.
| makeresults
| eval field1="test1", field2="test2", field3="test3"
| table [| makeresults | eval myfields="field1,field2,field3"| return $myfields]
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