[P5fRxh5kUvp2th]

I agree with your sentiment about REPL's, but there are two use cases where they're very useful.

1. When you need to explore behavior.

For example, C# has slicing syntax now. MyString[..15]. What happens when the string is only 8 characters long? Lets hit the REPL and find out.

2. Poking at systems using the same code as the rest of the codebase. For example, RoR. Being able to load up the RoR framework and poke at the ActiveRecord objects can be hugely helpful for tracking down an issue.