package Tie::Array::LastIndex;

# ...

use Carp 'croak';
use Exporter;
@EXPORT = qw( which what );

# ...

sub which (\@) {
  my $aref = shift;
  my $obj = tied @$aref;
  croak "which() only accepts arrays tied to " . __PACKAGE__
    unless $obj and $obj->isa(__PACKAGE__);
  return $obj->{INDEX};
}

sub what (\@) {
  my $aref = shift;
  my $obj = tied @$aref;
  croak "what() only accepts arrays tied to " . __PACKAGE__
    unless $obj and $obj->isa(__PACKAGE__);
  return $obj->{ARRAY}[ $obj->{INDEX} ];
}