perl XML::LibXML edit attribute

I am trying to open an XML file, change the value of a single attribute and then save it as another file. I want to use LibXml as this is a standard we use.
I have tried the following and many other combinations but cannot get it to work.

Can anyone help?

my $parser = XML::LibXML->new();
          my $tree = $parser->parse_file($file);
          my $root = $tree->getDocumentElement;
          my $meet_date = $root->getAttribute('meetingdate');
         

          my($node)  = $root->find('@meetingdate');
         $node->setData($meetingdate);

          print $tree->toString;


========== XML file stub ========
<?xml version="1.0" ?> 
- <meeting meetingdate="08 Sep 2010" meetingJetbetnumber="9" meetingType="GR"

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