use warnings;
use strict;

  my @alpha = qw(a b c d e f);

  my @location = qw(0 2 4);

   print $alpha[$_+1] for @location; # prints bdf
  
##</code><code>##

  my @alpha = qw(a b c d e f);

  my @location = qw(0 2 4 6 8 10 12);

  for (@location){
     print $alpha[$_+1] if defined $alpha[$_+1];
  }