I was just asking myself this same question. While I'm sure most of the comments below work just fine, I'd like to add my solution as well.

I just separated the "values" by a comma, and have a single "value" related to the key in my hash.

When I read out the key value, I'll just do a split on the value in order to break it up in to the individual data points I need.

This is simple, and very readable/easy to understand for someone who is not quite a perl monk like me.