macro_rules! path {
    (!$($rest:tt)*) => {{
        ::std::path::PathBuf::from(
            ::std::path::MAIN_SEPARATOR.to_string()
        ).join(path!($($rest)*))
    }};
    ($part:ident) => {{
        ::std::path::PathBuf::from(stringify!($part))
    }};
    ($part:ident / $($rest:tt)*) => {{
        path!($part).join(path!($($rest)*))
    }};
}

fn main() {
    println!("{:?}", path!(foo/bar/baz));
    println!("{:?}", path!(!usr/bin/sh)); // absolute
}