Манипулирование массивами массивов в Perl

Manipulating Arrays of Arrays in Perl

=head1 NAME

perllol - Manipulating Arrays of Arrays in Perl

=head1 DESCRIPTION

=head2 Declaration and Access of Arrays of Arrays

The simplest thing to build is an array of arrays (sometimes imprecisely
called a list of lists). It's reasonably easy to understand, and
almost everything that applies here will also be applicable later
on with the fancier data structures.

An array of an array is just a regular old array @AoA that you can
get at with two subscripts, like C<$AoA[3][2]>. Here's a declaration
of the array:

# assign to our array, an array of array references
@AoA = (
[ "fred", "barney" ],
[ "george", "jane", "elroy" ],
[ "homer", "marge", "bart" ],
);

print $AoA[2][2];
bart

Now you should be very careful that the outer bracket type
is a round one, that is, a parenthesis. That's because you're assigning to
an @array, so you need parentheses. If you wanted there I<not> to be an @AoA,
but rather just a reference to it, you could do something more like this:

# assign a reference to array of array references
$ref_to_AoA = [
[ "fred", "barney", "pebbles", "bambam", "dino", ],
[ "homer", "bart", "marge", "maggie", ],
[ "george", "jane", "elroy", "judy", ],
];

print $ref_to_AoA->[2][2];

Notice that the outer bracket type has changed, and so our access syntax
has also changed. That's because unlike C, in perl you can't freely
interchange arrays and references thereto. $ref_to_AoA is a reference to an
array, whereas @AoA is an array proper. Likewise, C<$AoA[2]> is not an
array, but an array ref. So how come you can write these:

$AoA[2][2]
$ref_to_AoA->[2][2]

instead of having to write these:

$AoA[2]->[2]
$ref_to_AoA->[2]->[2]

Well, that's because the rule is that on adjacent brackets only (whether
square or curly), you are free to omit the pointer dereferencing arrow.
But you cannot do so for the very first one if it's a scalar containing
a reference, which means that $ref_to_AoA always needs it.