The first six chapters from a book on CGI programming are available for free online or in .pdf format. Sample chapters cover getting started (writing scripts, uploading, etc.), Perl Variables, CGI Environment Variables, Processing Forms, Advanced Forms, and Reading & Writing Data Files. Source code from remaining chapters is also available.

Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers. A plain HTML document that the Web daemon retrieves is static, which means it exists in a constant state - a text file that doesn't change. A CGI program, on the other hand, is executed in real-time, so that it can output dynamic information.

CGI scripts allow you to add forms, and other user defined content to your pages. Writing a CGI program or script is similar to writing any other C program or Perl script. There are some things you should know, like how to display your results on a Web page, and how to debug. These links and articles will help you write your own CGI or get scripts for your site.