difference between a !~ b and !(a=~b)

Hi all, I wrote a conditional like this: `if !( A =~ B )`. It is not working, because I should have written `if A !~ B`. Fine. However, I wasn't getting any syntax error or anything, so it must have been doing something. As far as I understand, the first form should also work, shouldn't it? What is the difference? Why wasn't it working? Thank you