use Data::Dumper;

my $array_ref = [
                  [ qw/a b c/ ],
                  [ qw/d e f/ ],
                  [ qw/g h i/ ],
                ];

print Dumper $array_ref;

my $array_ref_b = [ 
                    [ qw/j k l/ ],
                    [ qw/m n o/ ],
                    [ qw/p q r/ ],
                  ];

print Dumper $array_ref_b;

unshift @$array_ref_b, @$array_ref;
print Dumper $array_ref_b