scoped_bindings() temporarily changes bindings in .env (which is by default the caller environment). The bindings are reset to their original values when the current frame (or an arbitrary one if you specify .frame) goes out of scope.
with_bindings() evaluates expr with temporary bindings. When with_bindings() returns, bindings are reset to their original values. It is a simple wrapper around scoped_bindings().
Pairs of names and values. These dots support splicing (with value semantics) and name unquoting.
The frame environment that determines the scope of the temporary bindings. When that frame is popped from the call stack, bindings are switched back to their original values.
An expression to evaluate with temporary bindings.
scoped_bindings() returns the values of old bindings invisibly; with_bindings() returns the value of expr.