How do I change text in a text file bundled with an app

I have done the following steps, and so far everything has worked.

1. Imported a text file into my project called test.xml

2. Ajax | Request test.xml (tag "testfile")

3. On "testfile" completed | Set variable to AJAX.LastData (if I could edit the text in the file directly, I could skip this step)

4. I make changes to variable using RegexReplace

Now I want to take the variable text and overwrite test.xml. How would I do this? I have seen some posts about node webkit, but this will be in an app. My last step will be to figure out how to send this file as an attachment in an email...but that's for another topic