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Re: printing all values in a hash of hashes of arrays

by GrandFather (Sage)
on Dec 15, 2014 at 19:51 UTC ( #1110401=note: print w/replies, xml ) Need Help??

in reply to printing all values in a hash of hashes of arrays

Hashes and array elements are scalar values so can only hold references to nested hashes or arrays. Therefore hash_of_hash_of_arrays{$outerkey} is a reference to a hash. To get the hash you need for keys you need to dereference it using %{}: %{$hash_of_hash_of_arrays{$outerkey}}.

Note that $, % and @ don't tell you what type variables are, they tell you what type of thing an expression returns. So $ref returns a scalar which may be a reference to an array or a hash. @$ref and @{$ref} return arrays (they are equivalent) by dereferencing $ref. The {} version is much clearer (and often required) when the expression used to get the reference is complicated.

Perl is the programming world's equivalent of English

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Re^2: printing all values in a hash of hashes of arrays
by BillKSmith (Parson) on Dec 15, 2014 at 21:08 UTC

    Perl's own documentation on this subject is very good. (Refer to the section "Using References" of perldoc perlref

    Grandfather is recommending rule 2 because it always works. The other rules are essentially "short cuts" which apply in special cases.

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