use strict; use warnings; use Data::Dumper;

my $x;
{
   my $x->{a}->[0] = "no you don't!";
}
{
   $x->{b}->[0] = "now you see";
}
print Dumper $x;

__END__
$VAR1 = {
          'b' => [
                   'now you see'
                 ]
        };