use strict;
use warnings;
use XML::Simple;

my $xfile = <<EOF;
<people>
    <person><name>Jane Doe</name><age>42</age></person>
    <person><name>John Doe</name><age>43</age></person>
    <person><name>Foo Bar</name><age>43</age></person>
</people>
EOF

my $people  = XMLin($xfile);

foreach (keys %{$people->{person}})
{
    my $person = $people->{person}->{$_};
    next if $person->{age} != 43;

    print "$_ is $person->{age}\n";
}

__END__
John Doe is 43
Foo Bar is 43