Most of the time if I'm doing this, it's in a git repo and I only want to affect the checked-in files so that I can easily diff my changes. So I use a combination of `git grep`, `xargs`, and `perl` via a script I named `git-gsr`:

https://gist.github.com/jaysoffian/0eda35a6a41f500ba5c458f02...

Put it in `PATH` and then: `git gsr <old> <new>`