You keep getting the same memory address of @array. No matter how many times you iterate, since all elements of @AoA refer to the same memory address, they all share the same value of @array, whatever its last content. Other than making array @array lexical, you can also assign anonymous array reference. Consider this,

#!/usr/bin/perl

use strict;
use warnings;

## first sample
print "---- 1. global \@array ----\n";
my(@aoa, @array);
for my $i (0..5) {
    @array = map { "#" x $_ } (0 .. $i);
    $aoa[$i] = \@array;
    print "$aoa[$i]\n"; # same memory address
}
print "@$_\n" for @aoa;

## second sample
print "\n---- 2. lexical \@array ----\n";
my(@AoA);
for my $i (0..5) {
    my @array = map { "#" x $_ } (0 .. $i);
    $AoA[$i] = \@array;
    print $AoA[$i], "\n"; # different memory address
}
print "@$_\n" for @AoA;

## third  sample
print "\n---- 3. anonymous array reference ----\n";
for my $i (0..5) {
    my @array =
    $AoA[$i] = [ map { "#" x $_ } (0 .. $i) ];
    print $AoA[$i], "\n"; # different memory address
}
print "@$_\n" for @AoA;
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Output,

---- 1. global @array ----
ARRAY(0x814f618)
ARRAY(0x814f618)
ARRAY(0x814f618)
ARRAY(0x814f618)
ARRAY(0x814f618)
ARRAY(0x814f618)
 # ## ### #### #####
 # ## ### #### #####
 # ## ### #### #####
 # ## ### #### #####
 # ## ### #### #####
 # ## ### #### #####

---- 2. lexical @array ----
ARRAY(0x818b03c)
ARRAY(0x814ed48)
ARRAY(0x8185ab8)
ARRAY(0x8185aac)
ARRAY(0x8185a58)
ARRAY(0x8185a40)

 #
 # ##
 # ## ###
 # ## ### ####
 # ## ### #### #####

---- 3. anonymous array reference ----
ARRAY(0x8183e38)
ARRAY(0x818b03c)
ARRAY(0x814ed48)
ARRAY(0x8185ab8)
ARRAY(0x8185aac)
ARRAY(0x8185a58)

 #
 # ##
 # ## ###
 # ## ### ####
 # ## ### #### #####
[download]

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