use threads qw(stringify);
use threads::shared;
my %contacts : shared;
##</code><code>##

$contacts{$contact} = &share( {} );
share( $contacts{$contact}{'a'} );
share( $contacts{$contact}{'inc_dnd'} );
share( $contacts{$contact}{'lock'} );
$contacts{$contact}{'a'} = 1;
$contacts{$contact}{'inc_dnd'} = &share( {} );
$contacts{$contact}{'lock'} = 0;

##</code><code>##

  DB<2> print Dumper $contacts{$user_id}
$VAR1 = {
          'inc_dnd' => {},
          'a' => '1',
          'lock' => '0',
          'd' => '/tmp'
        };

##</code><code>##

170:            lock( $contacts{$user_id} );
  DB<2> print is_shared($contacts{$user_id})
226839368
  DB<3> n
lock can only be used on shared values at get_contacts_pool_photos.pl line 170.
 at get_contacts_pool_photos.pl line 170
        main::get_contacts_pool_photos() called at get_contacts_pool_photos.pl line 93