Can homebrew update a formula and can it manage multiple versions?

I currently have Scala 2.9.0.1 installed and see that Scala 2.9.1 was released fairly recently. I want to upgrade. However, from what I'm seeing, I don't think homebrew supports upgrading formulae.

I see that "Multiple Version Support" is on the homebrew wishlist, but I wonder if this is up-to-date and/or much of an indication of future priorities for the project. I did a quick look at tickets in the ticket tracker but didn't see anything that jumped out at me.

In my case, I'm going to just install the new version and update my environment variables. That will work I suppose. But I feel like a package manager should help me clean up old versions if 开发者_StackOverflowI want it to.

Related links from the mailing list archives:

• I missed how to "brew upgrade outdated" or similar
• Making upgrades work properly

No to both (automatic updating and multiple version management) per https://github.com/mxcl/homebrew/wiki/Wishlist