Today, I began using regular expressions to change a whole bunch of code. However, what I learned from using RegEx in TextMate was not the same as in Visual Studio.
So, for example, the parenthesis around regular expressions to indicate a backreference in TextMate:
(\w+)
is represented by curly braces in VS:
{\w+}
And to get the backreference in TextMate, you would use the $:
$1
but in VS, you would use a backslash:
\1