Mastering Regular Expressions, 3rd Edition

7Perl

Perl has been featured prominently in this book, and with good reason. It is popular, extremely rich with regular expressions, freely and readily obtainable, easily approachable by the beginner, and available for a remarkably wide variety of platforms, including pretty much all flavors of Windows, Unix, and the Mac.

Some of Perl’s programming constructs superficially resemble those of C or other traditional programming languages, but the resemblance stops there. The way you wield Perl to solve a problem—The Perl Way—is different from traditional languages. The overall layout of a Perl program often uses traditional structured and object-oriented concepts, but data processing often relies heavily on regular expressions. In fact, I believe it is safe to say that regular expressions play a key role in virtually all Perl programs. This includes everything from huge 100,000-line systems, right down to simple one-liners, like

% perl -pi -e 's{([-+]?\d+(\.\d*)?)F\b}{sprintf "%.0fC",($1-32)*5/9)eg' *.txt

which goes through *.txt files and replaces Fahrenheit values with Celsius ones (reminiscent of the first example from Chapter 2).

In This Chapter

This chapter looks at everything regex about Perl,^† including details of its regex flavor and the operators that put them to use. This chapter presents the regex-relevant details from the ground up, but I assume that you have at least a basic familiarity with Perl. (If you’ve read Chapter 2, you’re already familiar enough to at least start ...