You can share nested hash, as long as the internal hashes are also marked as shared. Let's say your non-shared code to populate the hash looked like this: 
#non shared hash version
my %abc;

my @parents = qw( a b c );
my @children = qw( 1 2 3 4 );

for my $parent ( @parents )
{
  for my $child ( @children )
  {
      $abc{ $parent }{ $child } = 1;
  }
}

[download]
Changing the implicit hash creation to explicit hash creation will fix the problem. the perl thread model is predicated on non-shared data by default. This forces us to deliberately share all the structures. (It is a pain). 
# shared hash version.
my %abc : shared ;

my @parents = qw( a b c );
my @children = qw( 1 2 3 4 );

for my $parent ( @parents )
{
  unless (exists $abc{$parent})
  {
    my %p : shared;
    $abc{ $parent } = \%p;
  }
  
  for my $child ( @children )
  {
      unless ( exists $abc{$parent}{$child} )
      {
        my %c : shared;
        $abc{$parent}{$child}=\%c;
      }
      $abc{ $parent }{ $child } = 1;
  }
}

[download]
The lexical scopes for %p and %c will go away, but the references will remain in the hash, preventing garbage collection.

In reply to Re^3: Threading: Invalid value for shared scalar by spazm
in thread Threading: Invalid value for shared scalar by P0w3rK!d

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