New to ClearSilver, need pointers for Template Toolkit compatibility.

I am working on a project with 2 UI frameworks:

1) a legacy one with perl + Template Toolkit

2) a second one in PHP, where we are adpoting ClearSilver. 

While our future templates will be in cs, we have a body of older
templates in TT tags. It would be perfect if we can adapt the CS
grammar to be able to parse TT templates. Even a subset of the TT tags
will be good for us.

How hard is it to adapt or make configurable, the grammar / parsing
portion of cs? I notice cs_parse.c isn't using lex/yacc or some
parsing framework. How would you start doing something like this?

Thanks

XY