use threads;
use strict;
use warnings;
use PadWalker qw(peek_sub);


sub thr {
  my $xref = peek_sub(\&run_test)->{'$x'};
  print "\$xref in thr: $xref\n";
}

sub run_test {
  my $x = 1;
  my $xref = \$x;
  print "\$xref before thr: $xref\n";
  threads->create(\&thr)->join;
  $xref = \$x;
  print "\$xref after thr: $xref\n";
}

run_test;

##</code><code>##

$xref before thr: SCALAR(0x6c51a0)
$xref in thr: SCALAR(0x7584a0)
$xref after thr: SCALAR(0x6c51a0)