my $missing = sub {...};

# private sub
sub ugly_foo ($self, $foo=$missing->(), $bar=$missing->()) {
	say "foo is missing" if $missing->($foo);
	say "bar is missing" if $missing->($bar);
}

# compare with eq
sub uglier_foo($self, $foo=MISSING, $bar=MISSING) {
	# This comes from posting insufficiently tested code at midnight
	# say "foo is missing" if !$foo || $foo eq MISSING;
	# say "bar is missing" if !$foo || $foo eq MISSING;

	say "foo is missing" if $foo && $foo eq MISSING;
	say "bar is missing" if $bar && $bar eq MISSING;
}

# slurping
sub ugliest_foo ($self, @args) {
	my ($foo, $foo_missing);
	if (@args) {
		 $foo = shift @args;
	} else {
		$foo_missing = 1;
	}
	my ($bar, $bar_missing);
	if (@args) {
		$bar = shift @args;
	} else {
		$bar_missing = 1;
	}
	if (@args) {
		croak "too many arguments";
	}
	say "foo is missing" if $foo_missing;
	say "bar is missing" if $bar_missing;
}