Perl Regex 变量替换打印 1 而不是所需的提取

Question

案例一：

year$ = ($whole =~ /\d{4}/);
print ("The year is $year for now!";)

输出：年份是现在年份是 1！

案例二：

$whole="The year is 2020 for now!";
$whole =~ /\d{4}/;
$year =  ($whole);
print ("The year is $year for now!";)

输出：现在是 2020 年！现在！

有没有办法让 $year 变量只是 2020？

Answer 1

你得抓拍成团

$whole="The year is 2020 for now!";
$whole =~ m/(\d{4})/;
$year =  ;
print ("The year is $year for now!");

Answer 2

使用括号捕获匹配项，并一步将其分配给 $year：

use strict;
use warnings;

my $whole = "The year is 2020 for now!";
my ( $year ) =  $whole =~ /(\d{4})/;
print "The year is $year for now!\n";
# Prints:
# The year is 2020 for now!

请注意，我将此添加到您的代码中，以启用捕获错误、拼写错误、不安全构造等，从而防止您显示的代码来自运行:

use strict;
use warnings;

Answer 3

这是另一种捕获它的方法。这有点类似于@PYPL 的 .

use strict;
use warnings;

my $whole = "The year is 2020 for now!";

my $year;
($year = ) if($whole =~ /(\d{4})/);

print $year."\n";
print "The year is $year for now!";

输出：

2020
The year is 2020 for now!

Perl Regex 变量替换打印 1 而不是所需的提取

Perl Regex Variable Replacement printing 1 instead of desired extraction

regex

variables

perl

perl5.8