use strict;
use warnings;

use XML::Twig;

my $twig = do {
    my %seen;
    XML::Twig->new(
        twig_handlers => {
            'PERSON/NAME' => sub {
                my ($t, $e) = @_;
                $seen{NAME} = $e->text;
                check(\%seen);
            },
            'PERSON/AGE' => sub {
                my ($t, $e) = @_;
                $seen{AGE} = $e->text;
                check(\%seen);
            }
        }
    )
};

sub check {
    my $person = shift;
    return unless keys %$person == 2;
    print "$person->{NAME} is $person->{AGE} years old.\n";
    %$person = ();
}

for my $file (@ARGV) {
    $twig->parsefile($file);
}