version = x;

​

string derivedVersion(string derived, string[] baseVersions ...) {

    string str;

    foreach (i, base; baseVersions) {

        if (i != 0) { str ~= "else "; }

        str ~= "version("~base~") version = "~derived~";";

    }

    return str;

}

​

mixin(derivedVersion("x_y_z", "x", "y", "z"));

​

void main() {

    import std;

    version(x_y_z) writeln("worx");

}

​

​