UPDATE: I just got an email from the Template-Toolkit mailing list - please announce the other forums where you have asked your question in the future. It's just good Netiquette.

use strict;
use warnings;
use Template;

my $tt2 = Template->new;
$tt2->process(\*DATA, {
  AoA => [ [0,1],[2,3],[4,5] ],
  AoH => [ {a=>'b'},{c=>'d'} ],
});


__DATA__
AoA:
[% FOREACH outer_a = AoA -%]
[% FOREACH inner_a = outer_a -%]
[% inner_a %]
[% END -%]

[% END -%]

AoH:
[% FOREACH outer_h = AoH -%]
[% FOREACH key = outer_h.keys.sort -%]
[% key %] => [% outer_h.$key %]
[% END -%]

[% END -%]
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)