You can't really do that, although in theory, you could create different
Template::Parser objects that have different settings for INTERPOLATE, and compile different
Template::Document objects for your
Template::Provider objects to return. But that still wouldn't switch it on and off on a per-invocation basis.
What problem are you actually trying to solve? Maybe there's another way if you back up a step and tell us. Also, check the very helpful Template Toolkit mailing list (described at http://www.tt2.org).