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Perl for Web Site Management
book

Perl for Web Site Management

by John Callender
October 2001
Beginner content levelBeginner
528 pages
15h 20m
English
O'Reilly Media, Inc.
Content preview from Perl for Web Site Management

Taking It for a Spin

That’s a lot of information to digest at one sitting. Let’s put some of this into practice to help you get a better grasp of it. For this test drive, we’ll be using the script shown in Example 7-1.

Example 7-1. A simple script to demonstrate regular expression behavior

#!/usr/bin/perl -w

# regex.plx

# test regular expression behavior

$string = 'Walnuts are very nutritious.';

if ($string =~ /Walnuts/) {
    print "Match!\n";
} else {
    print "No match!\n";
}

Running this script should yield the following output:

[jbc@andros regex]$ regex.plx
Match!

This shouldn’t be terribly surprising. We’re looking for the literal string Walnuts, which occurs inside the string, so we have a match.

Let’s try out that fancy word-boundary backslash sequence \b. We can do that by modifying the line containing the regular expression in regex.plx to look like this:

if ($string =~ /Wal\bnuts/) {

Now when we run the script we should get the following:

[jbc@andros regex]$ regex.plx
No match!

The \b makes it so that the expression can no longer match, since it doesn’t have a word boundary between Wal and nuts.

Now change that \b to a \B (which says there isn’t a word boundary at that location):

if ($string =~ /Wal\Bnuts/) {

When we run the script it should give us:

[jbc@andros regex]$ regex.plx
Match!

Notice how the \B sequence doesn’t actually take up any space in the match. That is, /Wal\Bnuts/ can still match the string Walnuts, even though it has that \B sequence stuck in the middle of it. The ...

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Publisher Resources

ISBN: 1565926471Catalog PageErrata