No, a number of them are close to CYA such as CUL See You Later CUL8R, TTYL (Talk To You Later), BRB (Be Right Back). CUL and CUL8R mean that it will be returned later, whereas TTYL is more conscious and implies that there will be another conversation. BRB means a hiatus and not goodbye. CYA is the least complicated and the most informal form and thus it can be used in virtually any informal conversation or simple signature.