[misuba]

If you only want to write Swift, yeah. LT is supporting Python, JS, Clojure and ClojureScript. (And others?) And I don't know anything about editor extensibility in Xcode in general or Playgrounds in particular.

[muraiki]

Language support can be added via plugins. For instance, here's a Perl plugin: https://github.com/utsukushii/LT-Perl