while(@xyz) {
   my @copy = splice(@xyz,0,10);
   push @xyz_chunk, \@copy;
}

my @working;

while(@xyz_chunk) {
   my $xyz_chunk = shift @xyz_chunk;
   @working = @$xyz_chunk;
   print "debug: @working\n";
}

##</code><code>##

foreach my $val (@xyz_chunk)
{
   threads->create("sub", $val);
}