Why do you need to validate Perl generated XML? Are you not using one of the XML writing modules?

There are a large number of Perl modules available for working with XML. Of immediate interest may be XML::Twig, XML::Parser or XML::LibXML for validating XML documents. For writing XML there are a plethora of modules in various stages of creation. XML::Writer is probably a pretty good starting point.

It's hand rolled legacy XML, created by string concatenation. Thus, the need for a final "is it valid" check before shipping it off. I'm interested at this point only in validation -- not parsing, not XML generation.

The plethora of modules is a problem. What's the easy, simple, robust and mature recommendation on the best one to use?

It can validate XML against RelaxNG schemas also.

I like XML::LibXML for this. More at Re: HTML::Tidy question.

XML validation in Perl is a bit limited compared to other programming languages (IMHO). Besides the LibXML alternative suggested you might want to investigate XML::Validate. This looks like a promising initiative. I like the idea of a generic interface to different XML validation backends dependding on the platform you work on.

XML validation in Perl is a bit limited compared to other programming languages (IMHO)
Please elaborate, because the way I see it there is always

system qw[other-language-validate options file.xml  ];
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#!/usr/bin/perl -w
use strict;
use XML::Parser;
use XML::Checker::Parser;

my $xml = qq(<?xml version='1.0' encoding='iso-8859-1' ?>
<!DOCTYPE DISS_order SYSTEM 'umi_orders.dtd'>
<DISS_order>
</DISS_order>
);

my ($p1, $result);
$p1 = new XML::Checker::Parser();
eval {
    $p1->parse($xml);
};
if ($@) {
    print "Error\n";
}
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