Most modern languages have the concept of “libraries” that one can “import” and that can extend the language’s feature set.

For example, I don’t think C++ has such bit strings (the confusingly named bitset (https://en.cppreference.com/w/cpp/utility/bitset) comes close, but don’t think it does the substr and concatenation parts. basic_string<bool> has those, but not the Boolean operations), but they can be added when needed.

I believe both Ada and Common Lisp also share this ability, though Ada has nice support in its type system for doing things like mapping a portion of mmio register as bitstring that gets further defined as new type (whether enum, or integer, or string etc.)

If Ada has something like this, I haven’t seen it yet, but I’d be pleasantly surprised to learn otherwise.

I’ve heard about lisps having bitstrings support, but it was only briefly explained to me years ago and I haven’t seen it since.

Yes I also thought of Erlang bitstrings when I read that.

APL usually uses bitstrings, though that is an implementation detail.

Then, I guess APL is not exactly 'modern' anymore...