Perl中的错误：正则表达式中的嵌套量词

Question

Im a Perl noob and I have been trying to develop a simple script to capture some values from a regex. So far I have built the following program:

#!/usr/bin/perl

use strict;
$/ = '';

my $PM = qr{\b[A-Z][\w-]*\w};
my $de = qr{d[aoe]s?};
my $s = qr{[\n ]};
my $np = qr{$PM (?: $s $PM | $s $de $s $PM )*}x;

my $window_size = 7;
my $window = qr{($np) (?: $s+ (\w+))*};

while(<>){
  while(/($np) (?: $s+ (?: [\w-]+ | ($np))) ** {0..$window_size} /xg){
      print("\$1:  $1 and \$2: $2 \n");
  } 
}

However, when I try to run this code, it shows me the following error:

Nested quantifiers in regex; marked by <-- HERE in m/((?^ux:(?^u:\b[A-Z][\w-]*\w) (?: (?^u:[\n ]) (?^u:\b[A-Z][\w-]*\w) | (?^u:[\n ]) (?^u:d[aoe]s?) (?^u:[\n ]) (?^u:\b[A-Z][\w-]*\w) )*)) (?: (?^u:[\n ])+ (?: [\w-]+ | ((?^ux:(?^u:\b[A-Z][\w-]*\w) (?: (?^u:[\n ]) (?^u:\b[A-Z][\w-]*\w) | (?^u:[\n ]) (?^u:d[aoe]s?) (?^u:[\n ]) (?^u:\b[A-Z][\w-]*\w) )*)))) ** <-- HERE  {0..7} / at ./main.pl line 22, <> chunk 1.

Why is this not working?

EDIT: Im trying to use the ** operator as the general quantifier, followed by a range. I have read that it is equivalent to {range min, range max} quantifier

Answer 1

如果您不匹配带有“ **”的文字字符串，则需要对其进行转义。

/($np) (?: $s+ (?: [\w-]+ | ($np))) \*\* {0..$window_size} /