What is the difference between {} and ->{} in Perl? - arrays

Question

So if I have some data object and I want to access whats inside the element of that object
Whats the difference between
$Data{isEnabled})
$Data->{isEnabled}
my data is basically like this
for my $characterData (#{$AllCharacters->{'characters'}}) {
$Data{isEnabled})
$Data->{isEnabled}
and i want to access certain elements of my characterData but I'm not sure when to use
$Data{isEnabled})
vs
$Data->{isEnabled}
Like for example why does the first print work but the second fails?
use strict;
use warnings;
my %info = (NAME => "John", HOST => "Local", PORT => 80);
print $info{PORT};
print $info->{PORT};

Answer 1

The first expression accesses a key within a hash:
my %data = (is_enabled => 1);
print $data{is_enabled}), "\n";
In the second expression, data is not a hash, but a *hash reference. It would typically be declared as:
my $data = { is_enabled => 1 };
Since this is a reference, we need to use the dereferencing operator (->) to access the hash content:
print $data->{is_enabled}, "\n";
If you are iterating through an array of hashes, as your code seems to show, then each element is a hash reference. You need to use the second syntax:
my #all_data = ( { is_enabled => 1 }, { is_enabled => 0 } );
for my $data (#all_data) {
print $data->{is_enabled}, "\n";
}
You can read more about references in the perlref documentation page.

Answer 2

$Data->{isEnabled}
is equivalent to
${ $Data }{isEnabled}
I prefer the "arrow" notation, but it serves my explanation better to compare
$Data{isEnabled}
with
${ $Data }{isEnabled}
In the first case ($Data{isEnabled}), we are accessing an element of a hash %Data.
In the second case, we also appear to have a hash lookup, but we have a block ({ $Data }) where a name would normally be expected. It is indeed a hash lookup, but instead of accessing a named hash, we are accessing a referenced hash. The block (or the expression to the left of the ->) is expected to return a reference to the hash the program should access.
A reference is a means of referencing a variable through it's location in memory rather than by its name. Consider the following example:
my $ref;
if (condition()) {
$ref = \%hash1;
} else {
$ref = \%hash2;
}
say $ref->{id};
This will print $hash1{id} or $hash2{id} based on whether condition() returns a true value or not.