C/C++ compilers support multiple versions of the standards at the same time. You can compile one file with -std=c++98 and another with -std=c++17 and link them

C/C++ compilers support multiple versions of the standards at the same time. You can compile one file with -std=c++98 and another with -std=c++17 and link them together just fine. Rust is now doing the same thing with editions. Perl has 'use VERSION', but I'm not very familiar with it, not sure if e.g. new keywords only become available with that statement. The docs say 'use VERSION also lexically enables all features available in the requested version…'