Are you sure you are using the right module? The DOM objects look ... erm ... rather inconvenient to me. Assuming you parsed the XML using XML::Rules and used these rules:

   ...,
   'customDimensionName,customBucketValue' => 'content',
   'customBucket' => sub { '@'.$_[1]->{customDimensionName} => $_[1]->
+{customBucketValue} },
   'customBucketList' => 'no content',
   ...
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and already had in $cblIn a reference to the hash containing the bucket list, then getting the values would be just @{$cblIn->{$cbNameIn}}. And the memory footprint would be much smaller.