I think you're exaggerating the part about needing to change your data format. Template Toolkit can deal with pretty much any data structure you pass in, and doesn't need in-line Perl to do it.

You're right, that was unfair. Still, you end up catering to templating toolkits' notion of control structures no matter what, be they rigidly formatted data structures or a separate specialized in-line language. I'd like to code my control structures in Perl.