The following does what you want, although I don't think it's particularly pretty. I think that XML::Twig (as recommended by Cristoforo), or at least XML::LibXML would be much better. Note that both XML::XPath and XML::Twig use the same underlying parser, XML::Parser, which in turn uses Expat.
use warnings;
use strict;
use XML::XPath;
my $xml = <<'ENDXML';
<includes>
<include>
<priority>9990</priority>
<required>true</required>
<location>/efs/dist/tpcommon/itrstemplates/latest/common/templ
+ates/equities.xml</location>
</include>
<include disabled="true">
<priority>10001</priority>
<required>true</required>
<location>/efs/dist/itrs/tools/latest/common/templates/global_
+authentication.xml</location>
</include>
</includes>
ENDXML
my $xp = XML::XPath->new(xml => $xml);
my $nodes = $xp->find('//includes/include');
for my $include ($nodes->get_nodelist) {
for my $p ($xp->findnodes('./priority', $include)) {
my $priority = $p->string_value;
$p->removeChild($_) for $p->getChildNodes;
$p->appendChild( XML::XPath::Node::Text->new($priority+1) );
}
}
my ($root) = $xp->findnodes('/');
print $root->toString, "\n";
In regards to the last two lines above, I haven't yet found an easy way to print back out the XML document, maybe I'm missing something obvious. Anyway, for comparison, here's an XML::Twig solution:
use XML::Twig;
open my $ofh, '>', \my $outxml or die $!;
my $twig = XML::Twig->new(
twig_print_outside_roots => $ofh,
twig_roots => {
'/includes/include/priority' => sub {
my ($twig, $elt) = @_;
$elt->set_text( $elt->text+1 );
$elt->flush($ofh);
},
} );
$twig->parse($xml);
close $ofh;
print $outxml;
I've written some things a little longer than they need to be in this code for clarity, the code could be shortened quite a bit, and also the output doesn't need to go to a string, it could be sent to a file directly.