Just like it’s beneficial for the brain to learn several spoken languages, the same can be said about programming languages. The benefit might not seem big, but it adds up.
Each language has its own set of rules, of best practices, of approaches and paradigms. Learning more than one language will increase your ability to see a problem from different angles, to widen your perspective, to bring and apply principles from one language to another.
Adrian, in his post about being a developer over 40, gives advice as to learn a new programming every year and his approach is to build a simple calculator with whatever he learns — getting familiar with the IDE and APIs.
If you’re adventurous, you can go one step further and do some exercises, some katas or even a bit more complex apps. The point is to get in contact with it, go slightly beyond the very basics, to expand your knowledge.
In 10 years you might say ”7 of these languages are useless to me, I have never used them”, but the knowledge adds up as does the perspective widening. At the very least, your self-confidence that you can do it and that you did builds up. Lastly, if you wouldn’t have set out to learn new languages, you wouldn’t have learned the 3 that you found useful, either.
Keep learning; it’s a life-long process, with tremendous benefits.