use XML::LibXML qw();
XML::LibXML
    ->load_xml(string => <<'XML')->find('//dependency[not(version)]');
<project>
  <dependency>
            <!-- find all such dependency tags -->
            <groupId>com.solarmetric</groupId>
            <artifactId>kodo-jdo-runtime</artifactId>
  </dependency>
  <dependency>
            <groupId>javax.jdo</groupId>
            <artifactId>jdo</artifactId>
            <version>1.0.2</version>
  </dependency>

</project>
XML