I think the Waterbed Theory might apply. For example, I could explain Lisp syntax to my mother in fifteen minutes or so. It's very simple, just (f a b). However, the complexity that makes Lisp useful has to come out somewhere else. To be productive, she'd have to understand tree structures, code as data, car, cdr, list processing, and so on.
A language with simple syntax has to have a hefty standard library or it's not practically useful. The nice thing about syntax is that it's documented. In the case of Perl 5, we're talking about thousands of pages of standard documentation, indexed and searchable, organized by topic. Perl 6 will likely have similarly complete documentation.
Unless you're dealing with a program so very simple (or badly written) that it has no functions or modules or architecture, you're still at the mercy of the documentation or, failing that, the code itself. I'm not convinced you can really understand someone's code without reading it anyway.
If someone modifies the grammar in a Perl 6 module, you'll know. You'll have to read the grammar docs just as you would for any other library.