use Data::Dumper;

######################################
my @multi;
my $what_is_this = \$multi[1];
foreach my $i ( 10 .. 12 ) {
    foreach my $j ( 10 .. 12 ) {
        $multi[$i-10][$j-10] = "$i,$j";
    }
}
print Dumper $what_is_this;

print "\n\n";

######################################
my @multi2;
my $what_is_this2 = $multi2[1];
foreach my $i ( 10 .. 12 ) {
    foreach my $j ( 10 .. 12 ) {
        $multi2[$i-10][$j-10] = "$i,$j";
    }
}
print Dumper $what_is_this2;

print "\n\n";

######################################
my @multi3;
foreach my $i ( 10 .. 12 ) {
    foreach my $j ( 10 .. 12 ) {
        $multi3[$i-10][$j-10] = "$i,$j";
    }
}
my $what_is_this3 = $multi3[1];
print Dumper $what_is_this3;

__END__

$VAR1 = \[
            '11,10',
            '11,11',
            '11,12'
          ];


$VAR1 = undef;


$VAR1 = [
          '11,10',
          '11,11',
          '11,12'
        ];