> I thought that perhaps the simplest intermediate step would be to write a > new grammar for TT2 that parses our old grammar. Then we can migrate the > templates piece meal. (as no one has time to commit to working through > all the templates at once)
I'd recommend a different option: Have your old homegrown templates rewrite to TT2 code. I migrated from Text::Template, and I just wrote a Text::Template parser that converted it's tags to the cooresponding TT2 tags. I saved the new templates in a different directory tree, and was able to copy over the production templates as I tested them. We had a period where we ran two template systems, but on the whole the conversion was painless. (and TT2 is a much happier system)
