Mastering Perl

Chapter 11. Configuring Perl Programs

Once someone figures out that you know Perl, they’ll probably ask you to write a program for them or even change one of the programs that you have. Someone else finds out about your nifty little program and they want to use it too, but in a slightly different way.

Don’t get trapped into creating or maintaining multiple versions of your program. Make them configurable, and do it so your users don’t have to touch the code. When users touch the code, all sorts of things go wrong. Their little change breaks the program, perhaps because they forget a semicolon. Who do they come to for a fix? That’s right—they come to you. A little work making your program configurable saves you headaches later.

Things Not to Do

The easiest, and worst, way to configure my Perl program is simply to put a bunch of variables in it and tell the user to change them if they need something different. The user then has to open my program and change the values to change the behavior of my program. This gives the user the confidence to change other things, too, despite my warning to not change anything past the configuration section. Even if the user stays within the section where I intend her to edit code, she might make a syntax error. Not only that—if she has to install this program on several machines, she’ll end up with a different version for each machine. Any change or update in the program requires her to edit every version:

#!/usr/bin/perl use strict; use warnings; my ...