Add-ons • using Intercept & Modify HTTP Response

When using Intercept & Modify HTTP Response, how do I assemble the Search string to go with the replacement? If there are dozens of replacements to be done, do I put in wildcards to try to match up with the replacement? There was a file in the zip file called Help.js. What is that for? I can read the source code, but trying to follow what it is suggesting is not something I understand well. How is that file supposed to be used?