Writing CGI Applications with Perl

Sep 10, 2002 by Simon Cozens

It seems every month or so, there’s a new Perl and CGI book out; huge thick volumes promising to teach you all you need to know about programming for the Web in 24 hours. They all start with “Hello world” and they invariably finish with a shopping cart example. All this I find a little tedious.

Writing CGI Applications with Perl is not like this. Although, I have to admit, it has the obligatory shopping cart example. It starts on a firm footing - security, trustworthiness of user input and the environment, and tainting. Indeed, security is a recurrent - and a welcome - theme throughout the book.

Brent and Kevin are both well-known members of the Perl community, and the style and idiomatic nature of their code is second to none. If you learn Web programming from this book, then you’ll be learning quality code, guaranteed.

If I had to find the biggest criticism of this book, then it would be that its audience is quite unclear; you’ll need a reasonably firm basic knowledge of Perl to get the most out of it, and if your Perl is reasonably strong, then you may find the patient, line-by-line explanation of the code segments a little tedious. On the other hand, the beginner may enjoy this style of exposition, but become lost as the book progresses to more advanced subjects, such as the Perl DBI, graphics manipulation and mod_perl.

Another issue I have is that the organization of material isn’t particularly great - applications developed in the middle of the book use a backend database, but the DBI is only explained in a later chapter. However, I have to admit that if you stick to a strict order of introducing material, then the examples for the first half of the book end up being horribly contrived. Kevin and Brent have sacrificed a little linearity to end up with much more interesting, real-life applications.

What struck me most of all about this book was the clarity of presentation; both of the explanation of the code, but also of the physical layout of the book. A large left margin is perfect for scribbling notes, and the code stands out beautifully. Pulling together all of the code for a recap at the end of the chapter helps, too, except in the case of longer examples where you end up with pages of uncommented code.

However, some of the longer examples, particularly the full-chapter document management example (something that’s come in particularly handy when we’ve been developing a similar application ourselves … .) could do with many more screenshots so the reader can tell what the result is going to be.

I was impressed to find that the book covers the more practical areas of CGI programming - uploading your files to the server, debugging, testing off-line, dealing with Web caches and so on. There’s even a welcome section on how to read the Perl documentation. In fact, it was a bit of shame to look up the dreaded “premature end of script headers” error message in the index and not find an entry; but in real life, the entry for “debugging” pointed to a soultion that would work.

On the whole, the book covers the complete range of things you’re likely to be doing with CGI: from basic uses of the protocol, through file upload forms, using mod_perl, and the ever-popular Web page hit counter, right up to full-size production applications. In short, I’d consider this the book for those wishing to convert a little Perl experience into solid Web developer knowledge.

Writing CGI Applications with Perl is published by Addison-Wesley