my @data = (1, 2 ,3);
my $object = Foo->new;  # object supports method 'compute'
$tt->process('template.tt', {data=>[@data], object=>$object});

##</code><code>##

[% FOREACH d = data %]
The datum is [% d %] and the computed result is [% object.compute(d) %]
[% END %]