One of the answers to Why does ‘keys’ need a named hash? made me remember a question that's been bugging me for awhile.

duelafn replied with 

return keys %{ {map { $_ => 1 } @_} };

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I've been using this syntax and have accepted it as idiomatic Perl, however, what I don't get is, why the curly braces? And why two pairs of them? Is there a reference dereference happening?

Given this: 

say Dumper(\%{ {map { $_ => 'fish' } qw(one two red blue)} } );
             ^ ^                                         ^ ^
             |-|-----------------------------------------|-|

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I get: 
$VAR1 = {
          'blue' => 'fish',
          'one' => 'fish',
          'red' => 'fish',
          'two' => 'fish'
        };

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If I remove the inner pair of indicated braces, I get 
Ambiguous use of %{map{...}} resolved to %map{...}

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So the inner pair is a code block. I'm not sure that clears anything up for me, unless I'm being thick ...
If I need to return an array, as opposed to a list or a hash, what would that syntax be?
So if I want this: 

$VAR1 = [
          'one',
          'fish',
          'two',
          'fish',
          'red',
          'fish',
          'blue',
          'fish'
        ];

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How do I do it? 

say Dumper(\@{ {map { $_ => 'fish' } qw(one two red blue)} } );

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produces 
Not an ARRAY reference

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Which implies this is not a dereferencing thing ... unless of course I'm doing it wrong.

Thanks,
cbeckley

In reply to Syntax for casting map to a hash or an array by cbeckley

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