We introduce and discuss the opportunities of variable-length limited feedback systems where the quantized channel state information (CSI) is fed 
back from the receiver to the transmitter through binary codewords of possibly different lengths. We design and analyze the performance of the associated variable-length quantizers in various classical MIMO problem settings such as precoding/power control for maximum outage capacity/minimum error probability. We show that in many cases, a few bits of variable-length feedback can achieve the exact same gains of a system with perfect unquantized CSI. Therefore, variable-length feedback systems can significantly outperform their classical fixed-length
counterparts that require infinite rate to achieve the performance with perfect transmitter CSI.