To your question: yes, the Perl syntax (the macro system supports quasiquotation). This is exactly the same as in Lisp. The difference is that Lisp syntax looks more like how the data structures are represented in memory. I think you can also build up your programs with data constructors (i.e. like doing (list 'lambda (list 'x) (list '+ 'x 1)) in Lisp). But note that I haven't used Perl6, this is information from the web.
I wouldn't be surprised if sexprs are the end in the sense that the integers are. I.e. you might go on to discover new things but they'd ultimately reduce to sexprs.
Is there a textual representation for ASTs? Could you write programs directly in ASTs?