Drupal path pattern token if/then

I would like to do something like

if [node:subtitle] is available make the path pattern 
[node:title]-[node:subtitle]
else 
[node:titl开发者_开发知识库e]

What is the best way to do something like this?

---

You can't do it with the pathauto module I'm afraid, it simply doesn't have this functionality. You'd have to implement hook_node_presave() and change the path manually for each node you want to do this for.