Data::FormValidator inverse dependencies?

[meraxes]

Hello monks-of-unusual-size,

I've got a bit of a situtation with Data::FormValidator and a form... not sure what to do.

The form contains a checkbox called same_as_billing. If same_as_billing is checked that means re-use the billing address as the shipping address. Otherwise, I have to get shipping address information. That means I want Data::FormValidator to make some other fields required. Essentially, I want the inverse of the dependencies clause (since undef is not a valid hash key). So I know I can't do something like this:

dependencies => {
   'same_as_billing' => { undef => [ qw/street1 street2 city/ ] },    
}

I realize I could flip the meaning of the checkbox to be different_from_billing and I could easily do something like this:

dependencies => {
    different_from_billing => [ qw/street1 street2 city/ ],
}

... but Marketing dislikes the wording. Yay.

Manually tinkering with the POST/GET var before using Data::FormValidator is one way I could get around this by getting the inverse value but that seems messy and could confuse someone just looking at the code. Is there a way I can do this purely using DFV?

Many thanks,
meraxes