chromatic said

First of all, there's no "BNF grammar" in the interpreter. There's a parser and a lexer which you could, if you were enterprising enough, potentially represent in Backus-Naur Form, but it's not expressed as such anywhere within the Perl source code, and there is no singular representation of grammar within the Perl source.

I don't know much about the subject, but I'd be willing to believe that chromatic does.

You say "especially in use declarations", are you actually making a reference to the thread this answer came from?