Question

有人可以解释为什么我的循环不起作用吗？

#!/usr/bin/perl -w
use warnings;
use strict;
use URI;
use Web::Scraper;

my $url = "http://example.com";


# prepare data
my $scrapedata = scraper {
 process "div.something", 'pages[]' => '@rel';
};

# scrape the data
my $res = $scrapedata->scrape(URI->new($url));

# Get number of pages and define as var
for my $j (0 .. $#{$res->{pages}}) {
 my $varpages = $res->{pages}[$j];
  print "$varpages\n";
}


for ( my $count = 2; $count <= $varpages; $count++) {

print "$varpages\n";
print "$count\n";

}

这是错误：

# perl oli
Global symbol "$varpages" requires explicit package name at oli line 25.
Global symbol "$varpages" requires explicit package name at oli line 27.
Execution of oli aborted due to compilation errors.

Answer 1

$varpages的词法范围是代码块：

# Get number of pages and define as var
for my $j (0 .. $#{$res->{pages}}) {
 my $varpages = $res->{pages}[$j];
  print "$varpages\n";
}

稍后引用它的尝试引用了另一个变量。如果希望$varpages具有全局范围，请在分配给它的块之外声明它。例如：

my $varpages;
# Get number of pages and define as var
for my $j (0 .. $#{$res->{pages}}) {
  $varpages = $res->{pages}[$j];
  print "$varpages\n";
}

Perl简单循环

1 个答案: