There are many libraries you can use to manipulate files in perl and other languages. There are scripts to help you download HTTP and FTP files to be manipulated and include unescapers and form creators.
Another method of scripting on the web is to write applications/scripts that manipulate your HTML files periodically. This is useful for adding address to html files or creating automatic home pages.
Another interesting possibility is a script to modify HTML on the fly. You must modify or use features in some of the HTTP servers to do this. The advantage of this is that you can add addresses, pictures and other modifications on the fly.
CGI scripts do not have to be used with forms. Often a script can be called to display some type of calculation without anything to do with CGI. All you have to do is put them into the CGI-BIN directory and they should work. If you want to make them look better you need to add CONTENT Type and HTML code.