use strict;
use warnings;

BEGIN {
   package Testing;
   use Tie::Scalar qw( );
   BEGIN { our @ISA = qw(Tie::StdScalar); }
   sub STORE {
      my ($self, $val) = @_;
      print("STORE ", defined($val) ? "[$val]" : 'undef', "\n");
      shift->SUPER::STORE(@_)
   }
}

{
   our $s;
   tie $s, 'Testing';
   {
      print("pre\n");
      local $s;
      print("post\n");
   }
   print("\n");
   {
      print("pre\n");
      local $s = 'a';
      print("post\n");
   }
}