my $xml_ref = XMLin($xml, keyattr='');
[download]

[crash@shadowfax crash]$ ./this.pl
$VAR1 = {
          'QuestionList' => [
                              {
                                'Question' => {
                                                'Text' => 'Are dingos 
+your friend?',
                                                'Id' => '3',
                                                'Answer' => 'Satisfact
+ory'
                                              }
                              },
                              {}
                            ]
        };
Satisfactory[crash@shadowfax crash]$
[download]

If you dump $xml_ref you will find that the structure is not exactly what you think it is, xml_ref->{'QuestionList'} is an array ref, and what you want to display is $xml_ref->{'QuestionList'}->[0]->{'Question'}->{'Answer'};.

Sorry about the confusion, this is a snippet from a larger xml structure, I should have included more XML for the example. Try the following code instead:

#!/usr/bin/perl
use XML::Simple;
use Data::Dumper;

my $xml = qq|<?xml version="1.0" standalone="no"?>
<!DOCTYPE document SYSTEM "whocares.dtd">
<document>
    <QuestionList>
        <Question>
            <Id>3</Id>
            <Text>Are dingos your friend?</Text>
            <Answer>Satisfactory</Answer>
        </Question>
        <Question>
            <Id>3</Id>
            <Text>Should I have hit preview a second time?</Text>
            <Answer>Yes</Answer>
        </Question>
    </QuestionList>
    <QuestionList>
        <Question>
            <Id>11</Id>
            <Text>Should this run out of memory?</Text>
            <Answer>No</Answer>
        </Question>
    </QuestionList>
</document>|;

my $xml_ref = XMLin($xml);

print Dumper $xml_ref;
print $xml_ref->{'QuestionList'}->{'Question'}->[0]->{'Answer'};
[download]

in the full code I check to see if this is a list of questions or not... But if you try that one out Question indeed is an array ref as my print would suggest.

Then you are looking for:

$xml_ref->{'QuestionList'}->[0]->{Question}->[0]->{Answer}

I have found using the debugger pretty useful in such a case: once the XML had been XMLin'd, I x'd $xml_ref->{'QuestionList'}, saw it was an array, then x'd $xml_ref->{'QuestionList'}->[0], then $xml_ref->{'QuestionList'}->[0]->{Question} and figured out it was also an array... hence the final code. I often use this technique to debug complex data structures.

# the output from Dumper, s/\$VAR1/\$xml_ref/
$xml_ref ={
          'QuestionList' => [
                              {
                                'Question' => {
                                                'Text' => 'Are dingos 
+your friend?',
                                                'Id' => '3',
                                                'Answer' => 'Satisfact
+ory'
                                              }
                              },
                              {
                                'Question' => {
                                                'Text' => 'Should this
+ run out of memory?',
                                                'Id' => '11',
                                                'Answer' => 'No'
                                              }
                              }
                            ]
        };

print $xml_ref->{'QuestionList'}->{'Question'}->[0]->{'Answer'};
[download]

Note also, as I just have, that what you really want to do is

print $xml_ref->{'QuestionList'}->[0]->{'Question'}->{'Answer'};
[download]

I think that may solve your problem. Why Perl runs out of memory when you give it misleading deep nested references is another matter.

dave hj~

use strict;

my $ref;
$ref->{'hash'}->[0]->{'hash2'}->{'hash3'} = 'go go gadget autovivify!'
+;
print $ref->{'hash'}->{'hash2'}->{'hash3'};
[download]

While this:

use strict;

my $ref;
$ref->{'hash'}->[0]->{'hash2'} = 'go go gadget autovivify!';
print $ref->{'hash'}->{'hash2'};
[download]

I tried a couple of different combinations, the trick to making it barf is to have TWO or more levels of referencing after the one you reference incorrectly.

This is Perl 5.6.1 on Redhat Linux 7.2

/\/\averick
perl -l -e "eval pack('h*','072796e6470272f2c5f2c5166756279636b672');"

It's actually a pseudohash bug, fixed in 5.7.2 (5.8 to be).

Remember how pseudohashes work - they're actually arrays where the first entry is supposed to be a hash indicating the position of the fields. What's happening here is that perl is trying to create an enormous array. I can't recall the exact semantics of it, but it's something to do with extending the array to the size given by the length given by the memory location of "0", or something like that. Maybe someone can find the p5p discussion on this, so I don't have to look for it ;-)

Although this might not really be a solution for you, maybe it could help you until you find a better way.