I solved a problem of this kind at Re: Matching across newlines without stripping them out. That problem was simpler as it only preserved newlines (or any other characters), whereas you want to preserve tags. I don't recommend you to use it as it stands as HTML and regexes usually make a fragile combination, but it may provide some food for thought.

It's kind of a reversed approach of idsfa's Re^3: Munging Rendered HTML While Preserving Formatting.

Hope this helps,
ihb

In reply to Re: Munging Rendered HTML While Preserving Formatting by ihb
in thread Munging Rendered HTML While Preserving Formatting by Limbic~Region

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