According to the docs $received->parse_tree() returns a hashref. The example output shows that it is a hash of hashes (and in the case of comments a HoHoA). With that in mind the below shows how you might loop over such a structure and how to print just the 'domain' value of the 'by' hash.

You might also want to print your $header string (a better name than $string, by the way) to confirm that it is of a form acceptable to the module. 

#!/usr/local/bin/perl

use strict;
use warnings;

# snippet from docs
my $parse_tree = {
  'by' => {
    'domain' => 'host5.hostingcheck.com',
    'whole' => 'by host5.hostingcheck.com',
    'comments' => [
      '(8.9.3/8.9.3)'
    ],
  },
};

my $by = $parse_tree->{q{by}};

for my $key (keys %{$by}){
  print qq{$key -> };
  if ($key eq q{comments}){
    for my $comment (@{$by->{$key}}){
      print qq{$comment, };
    }
    print qq{\n};
  }
  else{
    print qq{$by->{$key}\n};
  }
}

print qq{\n\n};

print qq{by -> domain: $parse_tree->{q{by}}{q{domain}}\n};

[download]
outputs 
whole -> by host5.hostingcheck.com
domain -> host5.hostingcheck.com
comments -> (8.9.3/8.9.3), 


by -> domain: host5.hostingcheck.com

[download]

In reply to Re^3: Brief Hash Tutorial by wfsp
in thread Brief Hash Tutorial by gw1500se

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