First of all, you'll want to change your XML file since it is not valid: the second line lacks a DTD file name. The fourth and fifth line are not valid either. See the XML 1.0 specs for details. For simplicities sake I changed the document declaration to:

<?xml version="1.0"?>
[download]

leaving out the other lines.

The following code will parse the file and print the data you wish to extract.

#!perl

use strict;
use warnings;
use XML::Parser;

my $parser = new XML::Parser(Handlers => {'Start' => \&startHandler,
                                          'Char'  => \&charHandler,
                                          'End'   => \&endHandler});

my $mode = undef;

$parser->parsefile('data.xml');

sub startHandler {
    my $self = shift();
    my $element = shift();
    my %attributes = @_;
    if ($element eq 'LastTradePrice') {
        $mode = 'LastTradePrice';
    } elsif ($element eq 'NetChange') {
        $mode = 'NetChange';
    } elsif ($element eq 'LastTradeDate') {
        $mode = 'LastTradeDate';
    }
}

sub charHandler {
    my $self = shift();
    my $str = shift();
    if (defined $mode) {
        print "$mode: $str\n";
    }
}

sub endHandler {
    my $self = shift();
    $mode = undef;
}
[download]

Hope this helps, -gjb-