Perl Cookbook

Chapter 19. CGI Programming

Introduction

A successful tool is one that was used to do something undreamt of by its author.

—Stephen C. Johnson

Changes in the environment or the availability of food can make certain species more successful than others at getting food or avoiding predators. Many scientists believe a comet struck the earth millions of years ago, throwing an enormous cloud of dust into the atmosphere. Subsequent radical changes to the environment proved too much for some organisms, say dinosaurs, and hastened their extinction. Other creatures, such as mammals, found new food supplies and freshly exposed habitats to compete in.

Much as the comet altered the environment for prehistoric species, the Web has altered the environment for modern programming languages. It’s opened up new vistas, and although some languages have found themselves eminently unsuited to this new world order, Perl has positively thrived. Because of its strong background in text processing and system glue, Perl has readily adapted itself to the task of providing information using text-based protocols.

Architecture

The Web is driven by plain text. Web servers and web browsers communicate using a text protocol called HTTP, Hypertext Transfer Protocol. Many of the documents exchanged are encoded in a text markup system called HTML, Hypertext Markup Language. This grounding in text is the source of much of the Web’s flexibility, power, and success. The only notable exception to the predominance of plain ...