use strict;
use warnings;
use Data::Dumper;

my $a = [[0,1,2], [10,11,12]];
print \$a->[0][0], "\n";
print \$a->[0][1], "\n";
print \$a->[0][2], "\n";
print \$a->[1][0], "\n";
print \$a->[1][1], "\n";
print \$a->[1][2], "\n";
print "=======\n";
print \$_, "\n" for map @$_, @{$a};#one of your way
print "=======\n";
foreach (@$a) { print \$_, "\n" foreach @$_ }#your other way