printf("A float: %12" . ($root_beer ? ".4f" : "s") . $/, ($root_beer || ''));

##</code><code>##

if ($root_beer) {
  printf("A float: %12.4f$/", $root_beer);
} else {
  printf("A float: %12s$/", '');
}
##</code><code>##

printf("A float: %12s$/", $root_beer ? sprintf("%12.4f",$root_beer) : '');

##</code><code>##

my $root_beer_str = $root_beer || ''; # change 0 to blank.
$root_beer_str &&= sprintf("%12.4f", $root_beer);
printf("A float: %12s$/", $root_beer_str);

##</code><code>##

printf("A float: %12s$/", ($root_beer || '') && sprintf("%12.4f", $root_beer));