In Promise§
See primary documentation in context for method keep.
multi method keep(Promise:D: \result = True)
Keeps a promise, optionally setting the result. If no result is passed, the result will be True.
Throws an exception of type X::Promise::Vowed if a vow has already been taken. See method vow for more information.
my $p = Promise.new; if Bool.pick { $p.keep; } else { $p.break; }