Macro render 

macro_rules! render {
    ($write:ident, "{}" > $func:expr => $y:expr) => { ... };
    ($write:ident, "()" > $func:expr => $y:expr) => { ... };
    ($write:ident, "<>" > $func:expr => $y:expr) => { ... };
    ($write:ident, "[]" > $func:expr => $y:expr) => { ... };
    ($write:ident, call > $func:expr => $y:expr) => { ... };
    ($write:ident, echo > $x:expr $(, $i:ident = $z:expr)*) => { ... };
    (
        $write:ident =>
        $(
            $mode:tt > $x:expr
            $(=> $y:expr)?
            $(, $i:ident = $z:expr )*
        );+
        $(;)?
    ) => { ... };
}