package Your::Class;
our $VERSION= 1.001_001;

package Your::Class::_Implementation;

BEGIN {
    require constant;
    my $offset= 0;
    for my $member ( qw<
        _NAME _ADDRESS _PHONE ...
    > ) {
        constant->import( $member, $offset++ );
    }
}

sub Your::Class::new {
    ...
    $self->[_NAME]= ...;
}

##</code><code>##

...
package Your::CLass::_Implementation;

...

sub new {
    ...
}

...

package Your::Class;

BEGIN {
    require Exporter;
    for my $method ( qw<
        new ...
    > ) {
        Exporter::import(
            'Your::Class:_Implementation', $method );
    }
}

##</code><code>##

package Your::Class;
...
sub C'Name() { 0; }
...
package Something::Completely::Different;
...
sub C'Index() { 0; }
sub C'Name() { 1; } # Boom!
...