Macro cmd_lib_core::proc_env_set

macro_rules! proc_env_set {
    () => { ... };
    (&$env: expr) => { ... };
    (&$env: expr, $key:ident = $v:tt $($other:tt)*) => { ... };
    ($key:ident = $v:tt $($other:tt)*) => { ... };
}