use strict;
 use warnings;

##</code><code>##

- my @matrix = ( $n , $n );
+ my @matrix;

##</code><code>##

@array = (
  1,      2,       3,       <-- $i = 0
  4,      5,       6,       <-- $i = 1
  7,      8,       9,       <-- $i = 2
  ^       ^        ^
  |       |        |
  $j = 0  $j = 1   $j = 2
);

##</code><code>##

@array = (
  [ 1,      2,       3       ],  # <-- $i = 0
  [ 4,      5,       6       ],  # <-- $i = 1
  [ 7,      8,       9       ],  # <-- $i = 2
    ^       ^        ^
    |       |        |
    $j = 0  $j = 1   $j = 2
);

##</code><code>##

@array = ([ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]);
          ^^^^^^^^^^^  ^^^^^^^^^^^  ^^^^^^^^^^^
            $i = 0        $i = 1       $i = 2

# @array          = <nested_array1>, <nested_array2>, <nested_array3>;
# <nested_array1> = 1, 2, 3
# <nested_array2> = 4, 5, 6
# <nested_array3> = 7, 8, 9

##</code><code>##

@array = ( 5, 5 );

##</code><code>##

@array = ();

##</code><code>##

# $i = 0, $j = 0, $k = 1
@array = ( [ 1 ] );

##</code><code>##

@array = ( [ 1, 2 ] );

##</code><code>##

@array = ( [ 1, 2, 3 ] );

##</code><code>##

@array = ( [ 1, 2, 3 ], [ 4 ] );