Say you were applying at a well known, well regarded company. Eventually it progresses and they give you a programming test. A key part of that programming test are questions about a language you've never seen. For this example, it's a language so rare, that it might as well be an in-house language for which it is impossible to have any previous experience, even cursory.
The test lists operators and their functions, precedence, and the order of operations, and then provides a bunch of code that you have to decipher. However, the syntax, operators, and look of the code as a whole is fairly different from anything you've ever seen before.
They won't hire you if you can't learn the language on the spot.
How do you react?
Being a programmer isn't about knowing a specific language, it's about having the ability to solve problems.