#! perl -slw
use strict;
use Data::Dump qw[ pp ];
use XML::Simple;

# open DATA, '<', 'stream';

my $enc = <DATA>;
my $bot = my $top = <DATA>;
$bot =~ s[^<(\w+).*][</$1>]s;

my $section = '';
until( ( my $line = <DATA> ) =~ m[$bot] ) {
    my( $tag ) = $line =~ m[<(\w+)];
    my $end = "</$tag>";
    $section .= $line;
    $section .= <DATA> until $section =~ m[$end\s*$];
    my $ref = XMLin( $enc . $top . $section . $bot );
    ## do something with this section
    pp $ref;
    $section = '';
}

__DATA__
<?xml version="1.0" encoding="UTF-8"?>
<top>
    <sub name='1'>
       <subsub>
           some stuff
       </subsub>
    </sub>
    <sub name='2'>
       <subsub>
           some stuff
       </subsub>
    </sub>
    <sub name='3'>
       <subsub>
           some stuff
       </subsub>
    </sub>
    <sub name='4'>
       <subsub>
           some stuff
       </subsub>
    </sub>
    <sub name='5'>
       <subsub>
           some stuff
       </subsub>
    </sub>
</top>