Finding CGI Scripts   

No matter how much we try to persuade people that Perl is a multi-purpose programming language, we'd be deluding ourselves if we didn't admit that the majority of programmers first come into contact with Perl through their experience of CGI programs. People have a small web site and one day they decide that they need a guest book, a form mail script or a hit counter. Because these people aren't programmers, they go out onto the web to see what pre-written scripts they can find.

And there are plenty to choose from. Try searching on ``CGI scripts'' at Google. I found about two million hits. The first two were those well-known sites - Matt's Script Archive and the CGI Resource Index. Our web site owner will visit one of these sites, find the required scripts and install them on his web site. What could be simpler? See, the web is as easy as people make it out to be.

In this article, I'll take a closer look at this scenario and show that all is not as rosy as I've portrayed it above.

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  Why use CGI.pm   

One of Perl's greatest strengths is the CPAN, an archive of programs, scripts, snippets, and modules. These are all made available to other programmers worldwide, usually under the same terms as Perl itself. Just about anything that can be done with Perl is on the CPAN, or will be there shortly. (Some writers even find inspiration for columns and articles by watching the list of recent uploads.)

Because of (or contributing to) Perl's popularity as a language for web development and CGI programming, several CPAN modules handle everything from HTML formatting to CGI parameter processing. The grande dame is CGI.pm. Written by Lincoln Stein, it has the potential to make your CGI scripts shorter, more secure, more valid, and much easier to write. Even better, the CGI module has shipped in the core Perl distribution for several years. Any web host worth using will have it installed.

Unfortunately, many coders are not aware of the module's existence. Others don't see the need, as it's possible to write CGI programs in Perl without CGI.pm. Doing so, however, is similar to reading webpages through telnet instead of using a web browser. This may be a good learning experience, but it's fragile and very difficult to debug.

Two widely-used ``alternatives'' exist. One is cgi-lib.pl, an ancient Perl 4 libary. The other is a copied and pasted snippet of code that originated either in a web programming book or a free script. Both date back to the origins of the original CGI standard. While there are good alternatives to CGI.pm, these two solutions do not apply. They appear simple and effective, especially if they're familiar, but subtle and unsubtle bugs lurk underneath. Except in very specific cases, all new CGI programs written in Perl should use CGI.pm. This article explains three areas in which the module is superior to the other two common approaches.

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  Book Chapter - Sams Teach Yourself Perl in 21 Days, Second Edition (Part 1 of 2)   

Scalar data, as you learned yesterday, involves individual items such as numbers and strings. Yesterday, you learned several things you could do with scalar data; today, we'll finish up the discussion, show you more operators you can play with, and finish up with some related topics.

Go to Part 2

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  Book Chapter - Sams Teach Yourself Perl in 21 Days, Second Edition (Part 2 of 2)   

We'll finish up today with two topics that initially might not seem to fit with everything else we've talked about concerning scalar data: handling simple input and output. I've included them here essentially for one reason: so you know what's been going on in the scripts you've been writing that read input from the keyboard and print output to the screen.

Back to Part 1

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  Web Development with Apache and Perl   

In this chapter we'll discuss the different aspects of the web server, by which we mean both the physical machine and the program that responds to clients. It may seem somewhat confusing to mean two or more different things at different times, but the usage is normal in the industry. Context should make it clear when we mean hardware or software.

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  Autovivification : What is it and why do I care?   

During the growth curve of every Perl hacker they come to managing complex data structures like hash of hashes and lists of lists, etc. They usually get the hang of it with help from perllol, perldsc, some good books, usenet, #perl and whatever other resources they can find. But one subtle Perl feature seems to trip many of them up and that is the subject of this tutorial.

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  Function of the Month - grep   

Hi, and welcome to the first issue of my new column, ``Function of the month''. Every month, we'll begin by examining one of Perl's built-in functions and explore some ways to use it. From there, we'll take a broader look at how to solve some related problems in Perl and investigate any other Perl tricks and techniques we come across, just to remind you that there's always More Than One Way To Do It!

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  PerlWhirl 2000   

Have you ever been on a cruise? Have you ever been to a Perl conference? If so, just imagine enjoying both simultaneously.

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  yapc 19101   

A mere 2 weeks after returning from Perl Whirl 2000, I made a last-minute conference decision and was off again to yapc 19100 (Yet Another Perl Conference).

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  Beginning Perl : Ten Perl Myths   

Responses to the top 10 myths about Perl.

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