Perl cgi really is a lot of things, or combinations. Finding one book that covers any combination closely is not likely. As you can see from some of the other responses, you will need to check out html and javascript if you're not familiar with them already. There is a very good html reference, "Dynamic HTML: The Definitive Reference", you'll find use for that one, but it's not an introduction.

The hardest thing to figure out will probably be the indirection a webserver presents (here? there? serverside or clientside?) and on top of that the layers of a framework (how will the thread of execution flow through it all??) if you use that - understanding webserver and cgi will be a good start, but again, you need to check with your collegues what is used on your site, and if they have suggestions.