my %drink;
# other attribute hashes

sub set {
   my ($key, $attr, $value) = @_;

   my $hashref;
   eval "\$hashref = \\\%$attr";
   
   if ( !defined $hashref ) {
      carp 'Invalid attribute name';
   }
   else {
      $hashref->{$key} = $value;
   }
}