[snazz]

When you:

* can read gnarly real-world code with confidence

* know the stdlib and common libraries reasonably well

* have written something significant enough to be a good demonstration of your skills in that language, either at work or as a side project

Everyone with some programming experience knows that needing a refresher on a language you haven't used in a while is normal, so you can safely put languages on your resume that you used a while ago as long as you have brushed up on today's ecosystem.

As a general rule, the more senior you are, the more in-depth knowledge you'll be expected to have about anything you put on your CV. For that reason, splitting technologies up into a few different levels of proficiency is a good idea.