There can be more than one datafield and subfield, so you have to identify which one.

$data->{datafield}[$i]{subfield}[$j]{content}
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my $datafields = $data->{datafield};
foreach my $datafield (@$datafields) {
   my $subfields = $datafield->{subfield};
   foreach my $subfield (@$subfields) {
      my ($content, $code) = @{$subfield}{qw( content code )};
      ...
   }
}
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