sub SUBNAME($@;\%) This subroutine above is called with a scalar, array and followed by an optional hash...

Others, more worthy than I, have dealt with the hashref parameter. The @ does not mean an array, it means a list. Consider:

sub mysub($@\%) {
    my ($one, @two, $ref) = @_;
    print "@two\n";
}

mysub('a','b','c','d');
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Gives:

b c d
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The minimum length of a list is zero elements, so the following "works" (in that no error is reported) as well:

mysub('a');
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If you want to force an array, use \@. Prototypes are useful for forcing the correct type of reference being passed at compile-time (as opposed to runtime checks) but are so easy to circumvent, even accidently, that they can lull you into a false sense of security.