Call.sol

contract MyContract {    
    function callContract(address _addr, bytes _data) returns (uint8) {
      uint8 result;
      uint256 length = _data.length + 32;
      
      assembly {            
            let x := mload(0x40) // get empty storage location
            
            let ret := call (gas, 
                _addr,
                0, // no wei value passed to function
                _data, // input
                length, // input size
                x, // output stored at input location, save space
                0x01 // output size = 1 bytes
            )
                
            //result := mload(x)
            result := byte(0,x) // grab the first byte of x, since we are using uint8
            mstore(0x40, add(x,0x20)) // update free memory pointer
    }
    
    return result;
  }
}