如何在 Perl 正则表达式中提取第 n 个匹配项? [英] How can I extract the nth occurrence of a match in a Perl regex?

问题描述

是否可以从一串单引号中提取n^th个匹配项?

Is it possible to extract the n^th match in a string of single-quoted words?

use strict;
use warnings;

my $string1 = "'I want to' 'extract the word' 'Perl','from this string'";
my $string2 = "'What about','getting','Perl','from','here','?'";

sub extract_quoted { 

    my ($string, $index) = @_;
    my ($wanted) = $string =~ /some_regex_using _$index/;
    return $wanted;
}

extract_wanted ($string1, 3); # Should return 'Perl', with quotes
extract_wanted ($string2, 3); # Should return 'Perl', with quotes

推荐答案

你可以试试:

sub extract_quoted {

        my ($string, $index) = @_;
        while($string =~ /'(.*?)'/g) {
                $index--;
                return $1 if(! $index); # return $1 if index became 0. 
        }
        return; # not found - returns undef or () depending on context.
}

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