Regrettably, Perl does not have a clean distinction between classes and instances of said classes. As a result, class data is something that folks tend to forget about. One way of creating your set method is to store your class data in a hash.

my %CLASS_DATA = (...);

sub set {
  my ($self, %args) = @_;
  while (my ($var, $val) = each %args) {
    if (exists $CLASS_DATA{$var}) {
      $CLASS_DATA{$var} = $val; # whoops!  No validation
    }
    else {
      # create the var, croak, etc.
    }
  }
}
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If you don't like the validation, you could have each value in %CLASS_DATA be a sub ref that points to the real setter.

Personally, I've enjoyed Class::MethodMaker to handle much of this for me, though the recent test failures are disheartening.