how to detect unbalanced special characters in string

I'm wondering what would be the best way (likely using **grep** or **ack**) to return lines containing *unbalanced special character sets* in a string? For example, if the string were:

bqM#+t1U"OyBGhk]ozVG[v"&

and the specified character were a double-quote ("), this line would not be returned. However, what I'm looking for is more complicated, requiring a left and right balance, for instance a left square parenthesis ([) and a right square parenthesis (]). Then the line would be returned if the number of ([) does not equal the number of (]) such as:

i],U2y.2y[A~a`^[