use Data::Dumper;

$|++;


my %hash=(foo=>'bar',);

sub bar(){
  print "(".((caller(1))[3]||'main').")\n";
  print Data::Dumper->Dump([\%hash],['*hash']);
}

sub foo($) {
  local $hash{foo}="baz";
  bar();
}

foo bar, bar;
__END__
(main)
%hash = (
          'foo' => 'bar'
        );
(main::foo)
%hash = (
          'foo' => 'baz'
        );
(main)
%hash = (
          'foo' => 'bar'
        );