Here's how to do it:

1. Click on the button above to download and start the RegexFilenameChanger program via the Java Webstart Installer.

2. Once the program has started, you can use the Menu->Select directory to select the directory with the files you want to rename. The original names of the files in the selected directory appear in the left column of the main window.
3. You can edit the filenames using the textfields in the right column. Standard editor function like cut/copy/paste and mouse selection should work.

4. Use the textfield in the lower left to specify a regular expression that should be matched in the filenames. For example, _ matches a single underscore, while pattern matches the exact 7 character sequence, and a*b matches the longest sequence that begins with an 'a' and ends with a 'b'.
5. Remember to quote control characters like '.' and '[' by preceeding them with a backslash; e.g. write '\. ' to match a full-stop character followed by a space character.
6. Specify a replacement expression that should be used for each of the matched strings in the filenames. For example, enter the empty string to replace any occurance of the previously selected expression with nothing.
7. Press the Apply pattern button to change all filenames using the selected expression and replacement strings. Use Undo to undo the last change.
8. Repeat the above steps with a new expression and replacement, if necessary.

9. Finally, use the Rename files button to actually rename the files from their original names (left column) to the currently selected new names (right column).

   (Note: due to a bug, you can use the Rename-button only once. If necessary, use Menu->Select directory again to reenable the rename button for a given directory.)

Examples: not yet. Just play with the tool.