gistfile1.txt

class DefinedAlternationContainer { has $.item; has $.condition-was-defined };
sub infix:<?//>(\a, \b -->DefinedAlternationContainer) { with a { return DefinedAlternationContainer.new(item => b, condition-was-defined => True) };
DefinedAlternationContainer.new(item => Any, condition-was-defined => False) };
sub infix:<!!>(DefinedAlternationContainer:D \cont, \b){ cont ?? cont.item !! b };
my $v = 2 but False;
dd $v ?// 2 !! 4;
$v = Any;
dd $v ?// 2 !! 4;