I think you can tell quite a lot about someone by looking at code they've written.
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I've heard of 'blub languages', where you don't realise that other languages have better abstractions until you've experienced them.
I think the same thing happens with individual features. I've seen several C++ folks miss variadic generics in Rust, but I've not written enough C++ to feel it.
Over a sufficiently long time horizon, all code you write is legacy code.
I've added an eval button to the website of my programming language!
It's a been a lot of work to lock down appropriately. It still needs some UI polish but it's so nice to be able to try snippets immediately.
https://www.garden-lang.org/