Macro condu 

macro_rules! condu {
    ($g0:expr, $($g:expr),+;) => { ... };
    ($g0:expr;) => { ... };
    ($g0:expr, $($g:expr),+; $($rest:tt)*) => { ... };
    ($g0:expr; $($rest:tt)*) => { ... };
}

Condu! behaves like conda!, except that a successful line succeeds only once.