Much googling eventually turned up this interesting benchmark so I decided to give Text::MicroMason a whirl.
A quick trip to CPAN, an hour to convert the 150 line template from TT to MM syntax, and what do you know - identical output being produced in less than 10% of the time! The author says it all:
[Text::MicroMason] provides a reasonable subset of HTML::Mason syntax in a very light-weight fashion. In comparison to the other modules listed, MicroMason aims to be fairly lightweight, using one eval per parse, converting the template to an (sic) cacheable unblessed subroutine ref, eschewing method calls, and containing less than a thousand lines of Perl code.