If you can go the XML::Twig way, here is a piece of code that would work:

#!/usr/bin/perl

use strict;
use warnings;
 
use XML::Twig;

XML::Twig->new( twig_handlers => { customBucketEnd => \&end_bucket },
                pretty_print => 'indented',
              )
        ->parse( \*DATA)
        ->flush;

# assumes the customBucket and customDimensionName elements are ALWAYS
+ present
sub end_bucket
  { my( $t, $end)= @_;
    my @bucket_content;
    if( $end->prev_sibling( 'customDimensionName')->text eq 'Strategy'
+)
      { while(1) 
         { $end->cut;
           if( $end->tag eq 'customBucket') { last; }
           $end= $end->former_prev_sibling; # an obscure method that c
+omes in handy sometimes
         }
      }
    else
      { $t->flush; }
  }
    


__DATA__
<doc>
<customBucket></customBucket>      
<customDimensionName>Strategy</customDimensionName>
<customBucketValueString>Test1</customBucketValueString>
<customBucketEnd></customBucketEnd>
<customBucket></customBucket>
<customDimensionName>SubStrategy</customDimensionName>
<customBucketValueString>Test2</customBucketValueString>
<customBucketEnd></customBucketEnd>
</doc>
[download]