Perl is arguably the most popular scripting language in use today. It is used for a wide variety of tasks, including file processing, system administration, web programming, and database connectivity. Early Perl users had to be content with command-line interfaces or full-screen interfaces using Curses or similar systems, but the splitting-off of the Tk widget library from the Tcl language opened a whole new world to Perl. Perl programmers could now easily create graphical interfaces for their programs using Tk's flexible and friendly widget set and, with little effort, those programs could be made to work across Windows and Unix platforms.
The relatively recent advent of the web browser would seem to have made the Tk interface obsolete. CGI programs are almost inherently cross-platform and provide many of the same widgets as Tk (this includes Menus, Buttons, text entry fields, and so on). However, the inherent statelessness of the Web makes it difficult to write some programs for it. Perl/Tk provides a richer widget set than that available to the CGI programmer. Server push and client pull try to get around some of these limitations, while JavaScript fills in other gaps, but the fact is, the user experience still falls short in many instances. It is for precisely this reason that Perl/Tk continues to flourish.
The Tk module gives the Perl programmer full access to the powerful Tk widget set. This rich and diverse library, like Perl itself, makes the easy things easy and the hard things possible. Easy things include designing graphical interfaces with Buttons, Checkbuttons, Menus, and text entry fields—all of which you will learn about in the first half of this book. The second half of the book contains more advanced topics, such as creating custom widgets, interprocess communication, images, animation, and key bindings. The goal of this book is to take you from Tk neophyte to Tk expert.
