... pass an anonymous empty array to a subroutine:

&foo(qw());

A bit OT: I would say a better (because simpler) way to do this would be:
    foo();
What would be the purpose of the empty  qw() call?

BTW: I would also advise against using  & sigils for function calls in "modern" (i.e., post-4.xx version) Perl code; they will usually do no harm, but may introduce subtle bugs in certain cases (usually involving Prototypes — but let's just not involve prototypes!).