local() variables, on the other hand, are visible to routines that are called from the block where they are declared.

Not quite. It doesn't make the variables visible outside the block.

sub foo {
   ??? how do you access the var ???
}

{
   my %hash;
   local $hash{foo} = 123;
   foo();
}
[download]

It doesn't even create variables as your wording suggests. It's not that what you said is wrong, just unclear and/or misleading. (Compare to what I used earlier.)

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();
}
[download]

(Not that that's germane to the correct point you were making; just an interesting aside your ???s brought up :)

The cake is a lie.
The cake is a lie.
The cake is a lie.