September 2012
Beginner
744 pages
15h 48m
English
Content preview from Beginning PerlBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 8
Regular Expressions
WHAT YOU WILL LEARN IN THIS CHAPTER:
- Understanding basic regular expression matching
- Understanding substitutions, lookahead/lookbehind anchors and named subexpressions.
- Creating useful regular expression modules
WROX.COM CODE DOWNLOADS FOR THIS CHAPTER
The wrox.com code downloads for this chapter are found at http://www.wrox.com/remtitle.cgi?isbn=1118013847 on the Download Code I’ve replaced the tabs in the following code with spaces. Please review. The code for this chapter is divided into the following major examples:
- example_8_1_name_and_age.pl
- example_8_2_dates_pl
- listing_8_1_data_structure.pl
- listing 8_2_composed_regexes.pl
Sometimes instead of exactly matching text, you want to find some text that looks like something you’re expecting. This is where Perl’s regular expressions come in.
A regular expression is a pattern that describes what your text should look like. Regular expressions can get complex, but most of the time they’re straightforward when you understand the syntax. Regular expressions are often called regexes. (A single regular expression is sometimes called a regex or worse, a regexp).
An entire book can be (and has been) written on this topic. This chapter focuses on those aspects of regular expressions you’re most likely to encounter.
BASIC MATCHING
Say you have a list of strings and want to print all strings containing the letters cat because, like your author, you love cats.
my @words = ( 'laphroaig', 'house cat', 'catastrophe', ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.