+like($@, qr/^No\s+subroutine/, 'recall "" croaks');
+eval { recall \1 };
+like($@, qr/^Unhandled\s+SCALAR/, 'recall scalarref croaks');
+eval { recall [ ] };
+like($@, qr/^Unhandled\s+ARRAY/, 'recall arrayref croaks');
+eval { recall sub { } };
+like($@, qr/^Unhandled\s+CODE/, 'recall coderef croaks');
+eval { recall { 'foo' => undef, 'bar' => undef } };
+like($@, qr!exactly\s+one\s+key/value\s+pair!, 'recall hashref with 2 pairs croaks');