Note: this feature is experimental and not guaranteed to be backwards compatible or even exist at all in future Meson releases.
Meson now supports import std, a new, modular way of using the C++ standard library. This support is enabled with the new cpp_importstd option. It defaults to false, but you can set it to true either globally or per-target using override_options in the usual way.
The implementation has many limitations. The biggest one is that the same module file is used on all targets. That means you can not mix multiple different C++ standards versions as the compiled module file can only be used with the same compiler options as were used to build it. This feature only works with the Ninja backend.
As import std is a major new feature in compilers, expect to encounter toolchain issues when using it. For an example see here.