Convert hashref to array of kv pairs

Question

Here's my initial code:

sub my_sub {
    my $hash = {
        age => 5, # default value for "age" key
        @_        # the rest of the "hash" as an array
    };
    ...
}

#used like so:
my_sub("age" => 42, ...);

But I'd like to also support taking in a hashref in addition to an array. So I've tried:

sub my_sub {
    my $hash = {
        age     => 5, # default value for "age" key
        ref(@_) eq "" ? @_ : %{$_[0]}
    };
    ...
}

If you call it with an array like before, the ref(@_) eq "" check would be true and the conditional would evaluate to @_ like before. But I can't for the life of me get the false case to work. Currently, it says there are an odd number of elements in the anonymous hash. But when I print out the value of %{$_[0]} I see the expected flattened array of (age, 42, ...) - in other words it looks right in the context of printing it out, but it barfs when it's in the conditional, and I have no idea why. Halp.