Kristof Bastiaensen wrote:
> Hi,
> 
> I am wondering if this is the correct behaviour in gsub:
> 
> "bab".gsub(/(?!a)ab/, "cd")
> => "bab"
> 
> shouldn't that be "bcd"?

I think /(?!a)ab/ can't match anything. It's saying that the first 
character after the beginning of the match must not be "a", and the 
first character of the match must be "a". This is contradictory.