Search and replace.
This feature (*SAR) works with an empty template only. You can use it to prepare files for the main powerful renaming process. Select menu "tools->search and replace", enter what you want to change. All matches will be replaced. Press [Apply] to proceed. Here is an example to change all spaces in the name to underlines:
Search: " " (space, without ").
Replace: "_" (underline, without ").
File before: "very important document.txt".
File after: "very_important_document.txt".
If you need more sophisticated search and replace process or want to use other SR datatypes in the template along with *SAR, you should download RegExpSR plugin that works as an ordinary *XXV and also allows you to proceed with search and replace using regular expressions. The plugin available free of charge at the website.