Two questions for custom expression:

Two questions for custom expression:


1) Why the sample result for the custom expression only evaluates for columns? (see image) I am trying to debug a regular expression   RXReplace("The Small Red Fox has a small tail","Small","Big","gi")  

but in the same way, I can only see sample result If I replace the first argument with a column, but can't debug different scenareos



2) can I put comments in a custom expression?  


Image icon regex.jpg115.01 KB