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my @array = ( 1, 2, 3 );

for my $elem ( @array ){
    say $elem;
}

my $aref = \@array;

ARRAY(0x9bfa8c8)

for my $elem ( @{ $aref } ){
    say $elem;
}

my $x  = $array[0];

my $y = $aref->[1];

$array[1]  = "assigning to array element 2";

$aref->[1] = "assigning to array element 2";

my %hash = ( a => 1, b => 2, c => 3 );

...

    say "key: $key, value: $value";
}

my $href = \%hash;

while ( my ( $key, $value ) = each %{ $href } ){

    say "key: $key, value: $value";
}

my $x = $hash{ a };

my $y = $href->{ a };

$hash{ a }  = "assigning to hash key a";

$href->{ a } = "assigning to hash key a";

my @b = ( 1, 2, 3 );
my $aref = \@b;
...
for my $elem ( @b ){
    say $elem;
}

99
2
3

$b[0] = 99;
$aref->[0] = 99;

my @a = ( 1, 2, 3 );
my %h = ( a => 1, b => 2, c => 3 );
...

# assign a value to a single hash key through its ref
$h->{ a } = 1;