can't find v_xxxx_ in sentence

Hi.

Given the following sentence:
You are v_xx_ nice to help me with my problem.  It is very ?_xxxxxx_

I would like to find the v_xx_ strings and the ?_xxxxx_strings.
The target matches begin with a ?_ or v_ and end with a _
The "xxx" stuff is what could be dynamic.

I am using a regex of v_.*?_ to get the matches, but my results are not 
right.  I get a hodpodge of results, some right, some wrong.
For example, I will get a _you are_ not going to find this match_
It seems to pass the first _ in the string being evaluated.


Thanks.  I appreciate the help very much.  Especially since it's midnight now.