use strict;
use warnings;
use Template;
my $template = Template->new({
    INCLUDE_PATH => '.',
    EVAL_PERL    => 1,
    }) || die $!;

my $foo = foo(3,5);
my @s = ('this', 'that');

$template->process("tpl.txt", {foo => $foo, s => \@s}) || die $template->error();

sub foo { $_[0]+$_[1] }