MT::Template::Context->add_container_tag(KeyWordList => sub {
        my $ctx = shift;
        my $res = '';
        
        my $entry = $ctx->stash ('entry') 
      or return $ctx->error("No entry found.");
    
    return "" if (!defined $entry->keywords);
    my @keywords = split (/\s+/, $entry->keywords);
      
        my $builder = $ctx->stash('builder');
        my $tokens = $ctx->stash('tokens');
        
        foreach my $w ( @keywords) {
	            $ctx->stash('keyword', $w);
	            defined(my $out = $builder->build($ctx, $tokens))
	                  or return $ctx->error($ctx->errstr);
	            $res .= $out;
	        }
        $res;
    });

MT::Template::Context->add_tag(KeyWord => sub {
        my $ctx = shift;
        $ctx->stash('keyword');
    });