Many thanks for your help, Indeed $dat did contain the number. It now works as I wanted. What I believe was going wrong was that I was also calling the print command in various places, and with these print commands in place, it seems to stop working.

my $pageobj=$data->{page};
print @$pageobj;
delete $data->{page}[$dat];
print @$pageobj;
my $xmlO = $xml->XMLout($data);
open FILE, ">../services/xml/".$docid.".xml" or die;
print FILE $xmlO;
close FILE;
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This code does not work, but with the prints removed it does, so does calling print actually change the structure of the data structure? if so that would be good to know. Many thanks for your help, it working on yours meant I could focus my efforts away from thinking my syntax was wrong, and helped me find the real problem.