Please allow to use a backslash (\) instead of at-sign (@) at the beginning and end of files headers.
Example: \startditaa instead of @startditaa and \endditaa instead of @endditaa
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In the last beta: https://dl.dropboxusercontent.com/u/13064071/plantuml.jar PlantUML now accepts backslash and at-sign.So you can use @startXXX or \startXXX (same thing for end).Note that even if the modification has been done in the library, some plugins may not be working, because they might accept at-sign only, and not backslash. However, this should be fine with Doxygen.Tell us if it does not work for you!