use XML::Simple;

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

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

##</code><code>##

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";
}