I am afraid I am not understanding the syntax of hashes, particularly hashes that contain hashes. I am trying to use Mail::Field::Received. In particular the 'parse_tree' object. The documentation says it returns a hashref but the syntax in the example uses '$' rather than '%'. Here is my apparently syntactically incorrect code: 
# $string contains the 'Received' header
my $received = Mail::Field->new('Received',$string);
my $parse_tree = $received->parse_tree();
my $by = $parse_tree{'by'};
my $domain = $by{'domain'};

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The keys themselves are hashrefs. So if I wanted to extract the value of the key 'domain' which is part of the key 'by' from the parse_tree, how would I write the correct syntax and when do I use '%' vs. '$'? Thanks.

In reply to Brief Hash Tutorial by gw1500se

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