Unfortunately, Jeff (the Creator) has taken the Wiki off line, and I think that's where the list of key codes for the Send Keystrokes command was located. However, I have found a (poorly formatted) copy, where you can find all key codes with a bit of effort:
http://hi.baidu.com/caise/item/6b2edf0ee3313194a3df43b9
The code for the left bracket is [LBRACKET] . Have a good time with Stroke It!