You can convince OpenOffice to read the file and save the XML from the command line. You will have to write a few lines of code in the OpenOffice scripting language to do this. An example is in the paper on the web page that I referenced above 'Using Perl to Read and Write OpenOffice Documents.' See section #2 of the paper, 'Generating Web Banners' for example code and references for automating OpenOffice tasks.

For XML parsing I used XML::Twig. There are examples of how to do this in the paper. It is not hard, but XML is a large topic. You could easily use one of the many simpler XML modules for this task.

What you want to do is easy with this approach. For example, I wrote a program to extract the speaker notes from a PowerPoint presentation. See Section #1 of the paper for details. It took 20 minutes to implement the whole thing. Learning how to use this approach took much longer, but my paper should have enough to get you started.