sub test {
  my ($self, $x1) = @_;
  ...
};

sub startThread {
  my $self = shift;
  my $thr;

  share ($self->{x2});

  print "threads->create \$self{x1}=$self->{x1}\n";
  $thr = threads->create('test', $self, $self->{x1});
  $thr->detach();
}