sub mix {
  my ( $object, @classes ) = @_;
  push @classes, ref $object;
  my $package_name = join ( '_', @classes );
  my $package_list = join ( ' ', @classes );
  my $check = "package $package_name; \$declared";
  unless ( eval $check ) {
    print " -- creating new package $package_name -- \n";
    my $declaration =
      "package $package_name; use base qw($package_list);
       use vars '\$declared'; \$declared++";
    eval $declaration;
    die "declaration error: $@\n"  if  $@;
  };
  bless $object, $package_name;
}