look-around, including look-ahead and look-behind, is not supported

[hasanAjsf]

I'm trying to use regex with

let x = vev!["Control(?=[^s])", .. ] //# (?=[^s]) not ending with s

But got an error:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Syntax(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
regex parse error:
    (?i)Control(?=[^s])
               ^^^
error: look-around, including look-ahead and look-behind, is not supported
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
)', src/libcore/result.rs:999:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

[BurntSushi]

The error message is correct. It's not supported. This is also explained in the docs. I'm not sure what the purpose of this issue is?