gistfile1.txt

class DefinedAlternationContainer {
    has $.item;
    has $.condition-was-defined;
}

multi sub infix:<?>(\a, \b -->DefinedAlternationContainer) is export {
    with a { return DefinedAlternationContainer.new(item => b, condition-was-defined => True) }
    DefinedAlternationContainer.new(item => Any, condition-was-defined => False)
}

multi sub infix:<!>(DefinedAlternationContainer:D \cont, \b) is export {
	cont.condition-was-defined ?? cont.item !! b
}

my $falsish = 2 but False;
say $falsish ? 'defined' ! 'undefined';