my @keywords = ('this','that','other','foo','this',              
                   'bar');                      ^dupe


##</code><code>##

   my @keywords = ('this','that','other','foo','THIS',
                   'bar');                      ^uc(dupe)


##</code><code>##

   use strict;

   my (@keywords, %keywords);

   @keywords = ('this', 'that', 'other', 
                'foo', 'THIS', 'bar');
   @keywords{map lc,@keywords}=();
   @keywords = sort keys %keywords;

   foreach my $word (@keywords) {
           print $word . "\n";
   }