Optional group not working in regex

Question

I have the following strings:

"What version is installed on production server?"
"What appserver version is installed on production server?"
"What system version is installed on production server?"
"What os version is installed on production server?"

And the following regex:

 /(?:what|which).*(appserver|system)?.*version.*\son\s(\w*).*/i

I would expect to get appserver or system or undefined as the first matching group but I always get undefined .

If I remove the ? from the first matching group, I get appserver and system but the first and last string does not match anymore.

What is wrong?

See http://jsfiddle.net/ZVQTb/5/ for test bench.

Answer 1

The problem is that you're trying to look for anything up to "appserver" or "system", but when it's not there, there isn't another group before "version".

/(?:what|which).+?(appserver|system)?.*version.*\son\s(\w*).*/i

FIDDLE

Note: changed + to +? per Evan's keen eyes.