Right -- good solution. Like I said, there are easier ways to do it, but I'm curious if there is a way to do it with a single, one pass, global regex.

(I've actually implemented something similar to what you suggested just for the time being. At each line, I check for an existing altloc-atom name combo. If it exists, I skip the line, otherwise I update the hash with the new info. This gives me a single pass, though without the elegance of a regex)

Thanks!