Macro closure

macro_rules! closure {
    ( $( $x:ident $v:ident ),*; $y:expr ) => { ... };
}

Creates a closure-like block that performs variable rebinding before evaluating an expression. This macro takes a comma-separated list of identifier pairs, where each pair specifies a rebinding using a helper mechanism, and a trailing expression; it expands to a block that first applies the rebinding operations and then evaluates the provided expression within that modified scope.