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Perl in a Nutshell
book

Perl in a Nutshell

by Nathan Patwardhan, Ellen Siever, Stephen Spainhour
December 1998
Beginner to intermediate content levelBeginner to intermediate
674 pages
40h 41m
English
O'Reilly Media, Inc.
Content preview from Perl in a Nutshell

Regular Expressions

Regular expressions are used several ways in Perl. They’re used in conditionals to determine whether a string matches a particular pattern. They’re also used to find patterns in strings and replace the match with something else.

The ordinary pattern match operator looks like / pattern /. It matches against the $_ variable by default. If the pattern is found in the string, the operator returns true ("1"); if there is no match, a false value ("") is returned.

The substitution operator looks like s/ pattern / replace /. This operator searches $_ by default. If it finds the specified pattern, it is replaced with the string in replace. If pattern is not matched, nothing happens.

You may specify a variable other than $_ with the =~ binding operator (or the negated !~ binding operator, which returns true if the pattern is not matched). For example:

$text =~ /sampo/;

Pattern-Matching Operators

The following list defines Perl’s pattern-matching operators. Some of the operators have alternative “quoting” schemes and have a set of modifiers that can be placed directly after the operators to affect the match operation in some way.

m/ pattern /gimosx

Searches a string for a pattern match. Modifiers are:

ModifierMeaning
g

Match globally, i.e., find all occurrences.

i Do case-insensitive pattern matching.
m Treat string as multiple lines.
o

Only compile pattern once.

s Treat string as single line.
x Use extended regular expressions.

If / is the delimiter, then the ...

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Publisher Resources

ISBN: 1565922867Catalog PageErrata