Question: I understand that the /Developer folder no longer exists after installing XCode4.3. To me, this seems it would have bad consequences. First, CUDA installs into /Developer/GPU\_Computing. Second, what happens to the GCC keychain? Eclipse relies on the GCC keychain command line tools, which I'm told disappear with Xcode 4.3. 

Can someone shed light as to whether they have dealt with either of these problems?

Answer: 
That's it:

```
^(\d+,)*\d+$

```

The anchors `^$` will make the difference because they will force the whole string (not just a part) to match the pattern
You should try pattern like this:

```
^(?:(\d+),)+(\d)+$

```