Could you please add support for options such as 'delete_keys_undef'
and 'delete_keys_empty' that delete the keys of a parameter hash when
the values are undef or (undef or empty strings) respectively?
I'm asking this because Params::Validate can't be subclassed properly
because of things like
_get_options( (caller(0))[0] )
Side note:
That can be fixed too. To find the non-Params::Validate (or child
thereof) caller, one has to walk the caller frames until
UNIVERSAL::isa($package,'Params::Validate') returns 0. That's the
caller you need in that case.