C++ :: RValue - References As Return Values Of Functions

I am trying to understand RValue-references as return values of functions. First let's consider a simple function, that transforms a string into upper case letters.

const std::string
toUpper(std::string orig) {
std::transform(orig.begin(), orig.end(), orig.begin(), ::toupper);
return orig;

[Code] .....

It compiles, but I get the output 0 . Here I am wondering why the code above does not move the substr correctly while the code below does (prints out 1):

const std::string&&
no_sense(std::string abc) {
abc = abc.substr(1, 1);
return std::move(abc);

[Code] .....

In both cases abc is a temporary object inside of the function and gets deleted after the function is left. But why does the second version work and the first one does not?

cat.substr(1, 1)

And as my last question. Why doesn't

return std::move(abc.substr(1, 1));

work?