#!/usr/bin/perl

use XML::Simple;

local $/ = undef;
$xml_data = <DATA>;

    $xml_simple = XML::Simple->new( KeepRoot => 1,
                                     KeyAttr => 1,
                                  ForceArray => 1
                                  );
$xml_obj_data = $xml_simple->XMLin($xml_data);

use Data::Dumper;

print Dumper($xml_obj_data);

__DATA__ 
<OrderDetail>
       <ListOfItemDetail>
           <ItemDetail>
               <BuyerLineItemNum>1</BuyerLineItemNum>
               <ListOfStructuredNote>
                   <StructuredNote>
                       <GeneralNote>Line 1 Text.</GeneralNote>
                   </StructuredNote>
               </ListOfStructuredNote>
           </ItemDetail>
           <ItemDetail>
               <BuyerLineItemNum>2</BuyerLineItemNum>
               <ListOfStructuredNote>
                   <StructuredNote>
                       <GeneralNote>Line 2 Text.</GeneralNote>
                   </StructuredNote>
               </ListOfStructuredNote>
               <ListOfStructuredNote>
                   <StructuredNote>
                       <GeneralNote>More Line 2 Text.</GeneralNote>
                   </StructuredNote>
               </ListOfStructuredNote>
           </ItemDetail>
       </ListOfItemDetail>
</OrderDetail>