Yes, I have been scared, but that's during the college days. I used to write PHP, but then I started learning Java and basically loved the language, paradigms etc. I always thought that I would use both the languages so that I didn't forget PHP. However, I didn't get time to go back to PHP and continued writing Java. Eventually, I realised that you don't have to worry about forgetting how to code in a certain language. You should get better with time, learn new and interesting stuff. If you have to code in a certain language, you can always go back and brush-up your skills.

When I was a Java developer I used to believe that this was the language I would use for the next 5-10 years. But things changed, I moved to Node.js and have been working with it for last 3 years.

You never know what language you will end up using in next 5 years. So, master the one you are actively using and learn something new everyday.

You should worry more about what will come next before you focus on whether you remember how you previously did something.

Besides Perl, I have a pretty good memory for those things.

Perl is tricky to remember, thousands quirks to remember. I used to be some perl wizards a few years ago but I barely remember half of it now.