Documentation for method keep
Documentation for method keep, assembled from the following types:
multi method keep(Promise:)multi method keep(Promise: \result)
Keeps a promise, optionally setting the result. If no result is passed, the result will be
Throws an exception of type
X::Promise::Vowed if a vow has already been taken. See method
vow for more information.
my = Promise.new;if Bool.pickelse