Since you are only interested in certain nodes I'd look at mirod's XML::Twig. I'm trying to learn it myself but it sounds like it should do what you want. There is a tutorial for XML::Twig here
in reply to Will regex work here?
I think you can also do something like this using an XSL Transformation. It sounds like you want to transform your old XML into a new XML document, based on the value of the DATE attribute.
To do this you need a stylesheet and a transformation engine. There are many XSLT engines out there, you can use AxKit for an all-Perl solution or Xalan for a Java/Apache solution. There are many more that you can find here. I've been reading XSLT: Programmer's Reference for help on XSLT. It is really interesting stuff, but I'd look to XML::Twig and AxKit to help you get your job done today. When you have some time look at the other stuff.
I hope this helps.
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