$ perl -MTemplate -wE '
my $tt = Template->new;
my $compiled = $tt->template(\"In-place [% foo %] query\n");
my $answer = 40;
$tt->process( $compiled, {foo => $answer++} ) for 0..2;
'
In-place 40 query
In-place 41 query
In-place 42 query

##</code><code>##

my $tt = Template->new(
    INCLUDE_PATH => '/some/path',
    COMPILE_DIR  => '/other/path',
    COMPILE_EXT  => '.compiled',
);

my $file = 'foo.tt';
my $data = { foo => 42 };

$tt->process( $file, $data ) or die $tt->error;
# Template will be compiled and cached at '/other/path/foo.tt.compiled'
# and that file will be used until '/some/path/foo.tt' changes