use warnings;
use strict;
use XML::Twig;

my $twig = XML::Twig->new(
    pretty_print  => 'indented',
    twig_handlers => {
        jdk => sub {
            $_->set_text('JDK 1.8.0_40')->flush();
        },
    },
);
$twig->parsefile_inplace( 'nightly.xml', '.bak' );

__END__

<jdk>JDK 1.8.0_40</jdk>
<jdk>JDK 1.8.0_40</jdk>