Here's what I came up with... For each key in the structure, we provide the value we want for the default (if that key is missing). Then we work through the structure, replacing any undefined values with the desired default.

I'm not at all sure this is the kind of solution you want, (and I'm not entirely certain it even works like I think it does) but it was a lot of fun to tinker with it. :-)

use Data::Dumper;

# Trying to guarantee this:
#$self->{db}->{offer}->{product_id}->{name}

# We start with a fully formed hashref
$self->{db}->{offer}->{product_id}->{name} = 1;
# and undef somewhere in the middle
undef $self->{db};

# Show the structure just to prove it is too short
print Dumper $self;

my $Last = $self;
for (['db',{}], ['offer',{}], ['product_id',&func], ['name',42]){
  defined $Last->{$_->[0]} or $Last->{$_->[0]} = $_->[1];
  $Last = $Last->{$_->[0]};
}

print Dumper $self;

# func() is the default for key 'product_id' above
sub func{
  {}
}
[download]

prints:

$VAR1 = {
          'db' => undef
        };
$VAR1 = {
          'db' => {
                    'offer' => {
                                 'product_id' => {
                                                   'name' => 42
                                                 }
                               }
                  }
        };
[download]

Russ
Brainbench 'Most Valuable Professional' for Perl

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