This would mean that no FPM pool would be created unless a template path was provided? I'd like to keep it created by default ideally, so maybe need to set a default if `undef` above this? 

Could change the param to `fpm_pool` and:

````puppet
$fpm_pool_config = $fpm_pool ? {
  undef   => 'php/php-fpm-pool.conf.erb',
  default => $fpm_pool
}
````

Then if `false` no fpm pool would be created, and if defined as a custom value that would be passed through as the template path?