How use the keyword "as" in a custom DSL?

Hi all,

I'm writing a little DSL with Groovy mostly using the chaining method
technique.

Now, I wold like to use in my DSL the "as" keyword, but since it is a
Groovy keyword it is not so easy.

I've tried applying an AST transformation at conversion stage, but it is
too late because the AST is built taking in consideration the "as" keyword
as a cast operation, and so it's pretty complex to manipulate it to obtain
a method invocation AST tree.

Does anybody know a workaround or a different approach to write a DSL with
the 'as' keyword?

Thanks,
Paolo