Find and replace a specific character in tags?

I have been using Calibre for many years, and I literally just discovered hierarchical tags. :smack: I have nearly 5000 books tagged using non-hierarchical tags, with ">" in place of "." for genres and subgenres. For example:

nonfiction>science>physics

Is there a way to automatically find and replace all instances of ">" with "." in my tags column, or am I going to have to go through each entry and manually change them all? :eek:

Thanks,
mdclanahan