Mastering Modern Perl: Writing Efficient and Maintainable Code/

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Quantifiers

Quantifiers

Learn how to use regex with quantifiers in Perl.

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Matching literal expressions is good, but regex quantifiers make regexes more powerful. These metacharacters govern how often a regex component may appear in a matching string. The simplest quantifier is the zero or one quantifier, or ?:

Perl
use Test::More;
my $cat_or_ct = qr/ca?t/;
like 'cat', $cat_or_ct, "'cat' matches /ca?t/";
like 'ct', $cat_or_ct, "'ct' matches /ca?t/";
done_testing();

Any atom in a regular expression followed by the ? character means “match zero or one instance(s) of this atom.” This regular expression matches if zero or one a characters immediately follow a c character and immediately precede a t character. This regex matches the literal substrings cat and ct ...