Why are some hashes initialized using curly braces, and some with parentheses?

Question

I\'m looking at the following code demonstrating nested hashes:

my %HoH = (
    flintstones => {
        husband   => \"fred\",
        pal       => \"b         


        

Answer 1

First, the parens do nothing but change precedence here. They never have nothing to do with list creation, hash creation or hash initialisation.

For example, the following two lines are 100% equivalent:

{   a => 1, b => 2   }
{ ( a => 1, b => 2 ) }

For example, the following two lines are 100% equivalent:

sub f { return ( a => 1, b => 2 ) }    my %hash = f(); 
sub f { return   a => 1, b => 2   }    my %hash = f(); 

---

Second, one doesn't initialise a hash using { }; one creates a hash using it. { } is equivalent to my %hash;, except that the hash is anonymous. In other words,

{ LIST }

is basically the same as

do { my %anon = LIST; \%anon }

(but doesn't create a lexical scope).

Anonymous hashes allows one to write

my %HoH = (
    flintstones => {
        husband   => "fred",
        pal       => "barney",
    },
    jetsons => {
        husband   => "george",
        wife      => "jane",
        "his boy" => "elroy",
    },
    simpsons => {
        husband   => "homer",
        wife      => "marge",
        kid       => "bart",
    },
);

instead of

my %flintstones = (
    husband   => "fred",
    pal       => "barney",
);
my %jetsons = (
    husband   => "george",
    wife      => "jane",
    "his boy" => "elroy", 
);
my %simpsons = (
    husband   => "homer",
    wife      => "marge",
    kid       => "bart",
);
my %HoH = (
    flintstones => \%flinstones,
    jetsons     => \%jetsons,
    simpsons    => \%simpsons,
);