If you're interested, when I was working on a lib like this, each method had two versions, to* and as*, eg: $string->to_upper_case() # change the original

If you're interested, when I was working on a lib like this, each method had two versions, to* and as*, eg: $string->to_upper_case() # change the original $string->as_upper_case() # keeps original, and returns a new upper case string