parseNumeric

 //Numeric.RPL_KEYNOTSET
	import std.range : only, takeNone;
	import virc.common : User;

	with(parseNumeric!(Numeric.RPL_KEYNOTSET)(only("someone!test@example.com", "examplekey", "no matching key"), "@", "#").get) {
		assert(target== User("someone!test@example.com"));
		assert(key== "examplekey");
		assert(humanReadable == "no matching key");
	}

	assert(parseNumeric!(Numeric.RPL_KEYNOTSET)(takeNone(only("")), "@", "#").isNull);
	assert(parseNumeric!(Numeric.RPL_KEYNOTSET)(only("someone!test@example.com"), "@", "#").isNull);
	assert(parseNumeric!(Numeric.RPL_KEYNOTSET)(only("someone!test@example.com", "examplekey"), "@", "#").isNull);