How to remove separator characters if a token is empty?

I'm using the following tokens to generate an automatic node title:
[node:menu-link:parent:title]: [node:title] | [site:name]

But when [node:menu-link:parent:title] is empty the title will start with the colon separator (:). Is there a way to combine the separator with the token, so it's hidden when the token is empty?

Or where (template.php, custom module) can I alter the generated title to trim separator characters from the beginning of the title (and other meta tags)?