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Learning Perl, 5th Edition
book

Learning Perl, 5th Edition

by Randal L. Schwartz, Tom Phoenix, brian d foy
June 2008
Beginner content levelBeginner
352 pages
11h 16m
English
O'Reilly Media, Inc.
Content preview from Learning Perl, 5th Edition

Anchors

By default, if a pattern doesn’t match at the start of the string, it can “float” on down the string, trying to match somewhere else. But there are a number of anchors that may be used to hold the pattern at a particular point in a string.

The caret[*] anchor (^) marks the beginning of the string, while the dollar sign ($) marks the end.[] So the pattern /^fred/ will match fred only at the start of the string; it wouldn’t match manfred mann. And /rock$/ will match rock only at the end of the string; it wouldn’t match knute rockne.

Sometimes you’ll want to use both of these anchors to ensure that the pattern matches an entire string. A common example is /^\s*$/, which matches a blank line. But this “blank” line may include some whitespace characters, like tabs and spaces, which are invisible to you and me. Any line that matches that pattern looks just like any other one on paper, so this pattern treats all blank lines as equivalent. Without the anchors, it would match nonblank lines as well.

Word Anchors

Anchors aren’t just at the ends of the string. The word-boundary anchor, \b, matches at either end of a word.[] So you can use /\bfred\b/ to match the word fred but not frederick or alfred or manfred mann. This is similar to the feature often called something like “match whole words only” in a word processor’s search command.

Alas, these aren’t words as you and I are likely to think of them; they’re those \w-type words made up of ordinary letters, digits, and underscores. The ...

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Publisher Resources

ISBN: 9780596520106Supplemental ContentErrata Page