The old-string is replaced by the new-string in the name of each listed file. This WILL overwrite existing files. New-string may be "" to delete a substring of names.

Example:
	redub.csh .txt .html file.txt file2.txt redub.csh -0001 "" SAM_0477-0001.jpg
Resulting files
	file.html   file2.html   SAM_0477.jpg