Environment variable for application storage under OSX ?

[anonymous via Digitalmars-d-learn]

I have the following code, working under Win and Linux:
---
import std.process: environment;

immutable string p;

static this() {
    version(Win32) p = environment.get("APPDATA");
    version(linux) p = "/home/" ~ environment.get("USER");
    version(OSX) p = "?";
}
---

what would be the OSX equivalent (to get the path where the 
applications data are commonmly stored)?