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How do I make a hash of hashes?

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Contributed by vroom on Jan 12, 2000 at 00:35 UTC
Q&A  > Data Structures

Answer: How do I make a hash of hashes?
contributed by blackfrier

You can declare it like:

%hash = ( arms => { biggest => 'mine', smallest => 'yours' }, feet => { biggest => 'right', smallest => 'left' }, legs => { biggest => 'theirs', smallest => 'them', muscular => 'yes' } );
Answer: How do I make a hash of hashes?
contributed by chromatic

You can also add a hash by doing something like this:

$hash{toes} = { biggest => 'hairy troll', smallest => 'toddler', };
(Note that the {} make a reference to an anonymous hash. See perlman:perldsc for more gritty details.)
Answer: How do I make a hash of hashes?
contributed by Doraemon

This might interest you:

$other_hash{key} = ''; $hash{other} = \%other_hash; $hash{other}->{key} = '1'; # ok $tmp = $hash{other}; $$tmp{key} = '2'; # use it like this # $$hash{other}{key} = '2'; # but not like this ${$hash{other}}{key} = '3'; # this is ok $hash{other}{key} = '3'; # this too, -> unneeded after { +}
Answer: How do I make a hash of hashes?
contributed by da w00t

If it was declared as a named hash of multiple dimensions, you may access it like $hash{foo}->{bar}->{beer}="free";, or like this: $hash{foo}{bar}{beer}="free"; if you prefer to drop the arrows.

If it's an anonymous hash held in a hash reference, you access it like this:

$r_hash->{foo}{bar}{beer}= "free";

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