#!/usr/local/bin/perl

use warnings;
use strict;

init( [ qw/2 3 5 polka dot bikini/ ] );

my $index = 3;  #  'polka'
my ($current , $next , $prev ) =  get($index);

printf "%s\n%s\n%s\n"
  , $current , $next , $prev;


{ my ($old , $cursor , $size , @array);

  sub init
  { my $a_ref = shift;
    @array = @{$a_ref};
    $size = scalar @array or die "empty array\n";
    $cursor = 0;
  }

  sub get
  { $cursor = shift;
    $old = $cursor++;
    return ( current() , next_() , prev() );
  }

  sub current
  { return $array[$old];
  }

  sub prev
  { return ($old -1) >= 0 ?  $array[ $old -1 ] : undef;
  }

  sub next_
  { return ($old +1) < $size ? $array[ $old +1 ] : undef;
  }
}