RosettaCodeData/Task/Null-object/Tailspin/null-object-2.tailspin

// throws an error
def nothing: 0 -> mightBeNothing;

// throws an error
{ nothing: 0 -> mightBeNothing }

// OK, simply results in the empty structure without a field called 'nothing'
{ 0 -> mightBeNothing -> (nothing: $) }