I like your idea. It's well suited for the example situation. But...
It doesn't scale.
If you have a long list of fields to test, maybe an unknown number of fields, it makes sence to stop checking in the moment you find a mismatch.

This sub (that I use in a project) is both generic and scales well. It's not as Perlish beautiful as some examples, but it's quick. As you will see, it's part of a module.

########################################################
# Return true if all parameters are either defined or
# undefined. Return false if there is a mix.
########################################################
sub defined_all_or_none {
#my $self=shift; # This is a module, remember?
shift;

@_||(return 1);

if(defined($_[0])) {
   for(@_) {
      unless(defined) {
         return 0;
         }
      }
   }
else {
   for(@_) {
      if(defined) {
         return 0;
         }
      }
   }
1;
}
[download]

Update:
Seeing it on the screen made me see clearer. :-)
The statement:

my $self=shift; # This is a module, remember?
[download]

shift;
[download]

f--k the world!!!!
/dev/world has reached maximal mount count, check forced.

Edit Masem 2001-07-13 - Code Tags