Exactly. Although I've found it helpful to learn similar languages too (i.e. more than one scripting language). Seeing how subtle differences in the languages play out (beyond the superficial len/length type differences) has helped me understand some of the more subtle concepts of computer science. That said, you probably get the most bang-for-the-buck by picking up a language with a fundamentally different programming paradigm or at a lower or higher level than what you already know.