Perl simple loop

Question

Can somebody explain why my loop does not work?

#!/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";

}

This is the error :

# 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.

What value do you expect $varpages to have after leaving the first loop? — stark
– stark, Commented Dec 8, 2012 at 18:16
I want the value scraped from: process "div.something", 'pages[]' => '@rel'; — oliwiak82
– oliwiak82, Commented Dec 8, 2012 at 19:09

William Pursell · Accepted Answer · 2012-12-08 18:14:02Z

5

$varpages is lexically scoped to the code block:

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

The attempt to reference it later references a different variable. If you want $varpages to have global scope, declare it outside the block that assigns to it. For example:

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

answered Dec 8, 2012 at 18:14

William Pursell

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4 Comments

oliwiak82 Over a year ago

Hello, So I defined the $varpages var before the loop, and now I have the following error: Use of uninitialized value $varpages in numeric le (<=) at 6

William Pursell Over a year ago

That would certainly happen if $#{$res->{pages} is zero. Try initializing: my $varpages = 0;

Mauritz Hansen Over a year ago

Did you remove the 'my' from 'my $varpages' inside the for-loop, as William suggested?

oliwiak82 Over a year ago

Ups, I didn't. That was the problem. Thanks for this and for William also for pointing the problem.

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