Problem with using variable in <?cs include: ?>

Hello,

I've got a problem with using variable in <?cs include: ?> in template.

I can include file
<?cs include: "path_to_file/file.tmpl" ?>

I've defined in perl script:
$hdf -> setValue("Page.Template.Menu", "path_to_file/file.tmpl");

In template, I can also print variable containing full file name with:
<?cs var:Page.Template.Menu ?>

I'd like to use this variable in include.
None of these works:
<?cs include: Page.Template.Menu ?>
<?cs include: $Page.Template.Menu ?>
<?cs include Page.Template.Menu ?>
<?cs include $Page.Template.Menu ?>

Have you got any idea what can be wrong?

Thanks for any tips.

Pev