#! perl -slw
use strict;
use threads;
use threads::shared;
use Data::Dump qw[ pp ];

sub helper {
    my $ref = shift;
## Not needed if no more that one thread will access each subhash
##    lock $ref;         
    $ref->{NEW_KEY} = 1;
}

sub my_sub {
    my $ref = shift;
    my @threads = map async( \&helper, $_ ), values %{ $ref };
    $_->join for @threads;
}

my $hoh = {
    A => shared_clone( { NAME => 'aa' } ),
    B => shared_clone( { NAME => 'bb' } ),
};

pp $hoh;
my_sub( $hoh );
pp $hoh;

##</code><code>##

C:\test>junk39
{
  A => {
         # tied threads::shared::tie
         NAME => "aa",
       },
  B => {
         # tied threads::shared::tie
         NAME => "bb",
       },
}

{
  A => {
         # tied threads::shared::tie
         NAME => "aa",
         NEW_KEY => 1,
       },
  B => {
         # tied threads::shared::tie
         NAME => "bb",
         NEW_KEY => 1,
       },
}