c++ - Again on typename and template keywords

I have carefully read many answers concerning this topic, but nevertheless I cannot figure out EXACTLY when these two keywords ARE or AREN'T needed in the scope of a non-template function which is member of a nested template class.

My reference compilers are GNU g++ 4.9.2 and clang 3.5.0.

They behave hardly different on the following code where I put embedded
comments trying to explain what happens.

#include 

// a simple template class with a public member template struct
template 
class Pa
{
// anything
public:
    template 
    struct Pe  // a nested template
    {
        // anything
        void f(const char *); // a non-template member function
    };

    template  friend struct Pe;
};

// definition of the function f
template 
template 
void Pa :: Pe :: f(const char* c)
{
    Pa p; // NO typename for both clang and GNU...

    // the following line is ACCEPTED by both clang and GNU
    // without both template and typename keywords
    // However removing comments from typename only
    // makes clang still accepting the code while GNU doesn't
    // accept it anymore. The same happens if the comments   of template
    // ONLY are removed.
    //  
    // Finally both compilers accept the line when both typename AND
    // template are present...
    /*typename*/ Pa::/*template*/ Pe q;

    // in the following clang ACCEPTS typename, GNU doesn't:
    /*typename*/ Pa::Pe qq;

    // the following are accepted by both compilers
    // no matter whether both typename AND template
    // keywords are present OR commented out:
    typename Pa::template Pe qqq;
    typename Pa::template Pe  qqqq;
    std::cout << c << std::endl; // just to do something...
}

int main()
{
    Pa::Pe pp;
    pp.f("bye");
}

So, in the scope of f is Pa::Pe a dependent name or not?

And what about Pa::Pe ?

And, after all, why this different behaviour of the two quoted compilers?

Can anyone clarify solving the puzzle?