There's also "slow compared to C" and "slow enough that you notice when using it as an interactive shell". Running something like `Dir.each_child('.') {|x| p x}` in the interpreter completes in 1.3 milliseconds, which includes all the separate print calls. It could be much faster if we compute the string to print first and then only issue a single print call, but this is deliberately inefficient to show it doesn't matter in this usecase.

I wouldn't use Ruby for high performance computing. But for scripting (where runtime is not critical), web services (where transport latency will usually far outstrip the few milliseconds your handler takes) or shell use (where humans aren't fast enough to issue a new command every millisecond anyway), Ruby is more than fast enough.