around BUILDARGS => sub {
   my $orig = shift;
   my $class = shift;
   ...
   return $class->$orig(...);
};

##</code><code>##

sub new {
   my $class = shift;
   ...
   return $class->SUPER::new(...);
}

##</code><code>##

has attr => (
   reader => '_get_attr',
   writer => '_set_attr',
   handles => {
      get_attr => sub { ... },
      set_attr => sub { ... },
   },
)