Of course if you resort to minor evil there is a way to get at it . . . :)

use PadWalker qw( peek_my );

sub foo {
  my $ebil = peek_my( 1 );
  print $ebil->{'%hash'}->{foo}, "\n";
}

{
   my %hash;
   local $hash{foo} = 123;
   foo();
}
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(Not that that's germane to the correct point you were making; just an interesting aside your ???s brought up :)