Inside-out accessor methods - version 2

This solution uses a hash of hash-references, which means we no longer need the nasty eval. With thanks to the perl monks.

my (%speed, %reg, %owner, %mileage);
my %hashrefs = ( speed   => \%speed,
                 reg     => \%reg,
                 owner   => \%owner,
                 mileage => \%mileage);
                   
sub set {
   my ($self, $attr, $value) = @_;
   my $key = refaddr $self;
     
   if ( !exists $hashrefs{$attr} ) {
      carp "Invalid attribute name $attr";
   }
   else {
      $hashrefs{$attr}{$key} = $value;
   }
}