Perl正则表达式：计算领先的子串

Question

是否有可以计算子字符串出现在另一个字符串开头的频率的Perl正则表达式？

例如

my $string = "../../../../../../../../../Downloads/../Testing/../";

my $countstr = "../";

结果应该是9，因为在../的开头有9次出现$string。

Answer 1

您可以使用全局正则表达式和\G锚点执行此操作，如此

use strict;
use warnings;

my $string   = '../../../../../../../../../Downloads/../Testing/../';
my $countstr = '../';

my $n = () = $string =~ /\G\Q$countstr/g;

print $n, "\n";

<强>输出

9