Here is a way to make it work, which only creates a single XML::Twig object in the thread, then reuses it. (Also its 'use threads', not 'use Thread'. I made it as simple as I could for clarity. Threads need to go to the end of their code block in order to be joined, but a return will work as well. Anyways, this creates 1 thread, and 1 XML::Twig object, then reuses it.

#!/usr/bin/perl
use warnings;
use strict;
use threads;
use threads::shared;

my $tgo;
my $tdie;
my $tfile;

share $tgo;
share $tdie;
share $tfile;

$tgo = 0;
$tdie = 0;
$tfile = ''; 
my $thread = threads->new(\&querySystem);

foreach my $file('xmlfile.xml', 'xmlfile.xml' ){
        $tfile = $file;
        $tgo  = 1;
        sleep 5;
      }

$tdie = 1;
$thread->join;
print "done press any key to exit\n";
<>;
###################################################

sub querySystem
{
        use XML::Twig;
        $|++; 

        my $statusTwig = new XML::Twig(
               twig_roots => {'Result/Status' => sub{
                           my($twig, $element) = @_;
                           my $mmsVersion = $element->first_child('MMS
+Version')->text;
                           my $partVersion = $element->first_child('Pa
+rticipantVersion')->text;
                           print "mmsVersion: $mmsVersion, partVersion
+: $partVersion\n";
       
           } }, 
               ProtocolEncoding=>"x-sjis-unicode");

       while(1){
            if($tdie == 1){ goto END }; 
      
              if ( $tgo == 1 ){
             
              my $result = $statusTwig->safe_parsefile($tfile);
              $tgo = 0; #turn off self before returning      
       }else
         { sleep 1 }
    }
END:
}

__END__
[download]