This snippet uses XML::Simple to solve your problem as I understand it.

use XML::Simple;

my $monk = XMLin('./monk.xml', 
  keyattr => {val => 'val1'}, 
  forcearray => ['val']
);

if($monk->{vals}->{val}->{FOO}) {
  print $monk->{say}, "\n";
}

[download]

That's not to say XML::Simple will handle all your XML parsing needs but it can do the simple stuff. For more complex stuff the options boil down to using a SAX parser or an XPath-capable DOM module (or XML::Twig for a more Perlish API).

As you found, maintaining state when you use XML::Parser's handler API involves storing stuff in global variables (or using a closure if you're that way inclined). This is one of the reasons that the XML::Parser API is effectively deprecated in favour of XML::SAX which uses a cleaner object oriented style. However, with SAX you'll have the same problem you found with XML::Parser - having to write pages of code to perform a seemingly simple task.

The other option is to use XML::XPath or XML::LibXML to slurp the XML file into a DOM tree which you can query with XPath statements. eg:

use XML::XPath;
use XML::XPath::XMLParser;

my $xp = XML::XPath->new(filename => './monk.xml');

my $nodeset = $xp->find('/monk[./vals/val[@val1 = "FOO"]]');

foreach my $node ($nodeset->get_nodelist) {
   my $say = $xp->findvalue('./say', $node);
   print "$say\n";
}

[download]

XPath is kind of a regex for XML syntax. The $xp->find statement returns a list of nodes which match the XPath expression (in this case all 'monk' elements which contain a 'val' element in a 'vals' element, where the 'val' element has a 'val1' attribute containing the string 'FOO'). The $xp->findvalue is then used to extract the contents of the returned node's 'say' child element.

For more info, see the Perl-XML FAQ.

Using regexes is not a great idea because although you can create something that works in simple cases it's really hard to cover all your bases (eg: what if the XML contains a numeric character entity or is UTF-16 encoded). To see just how hard it is to do it right, take a look at the source of XML::SAX::PurePerl.

In reply to Re: XML::parser question by grantm
in thread XML::parser question by semio

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