ReadKey MODE [, Filehandle] Takes an integer argument, which can currently be one of the following values: 0 Perform a normal read using getc -1 Perform a non-blocked read >0 Perform a timed read (If the filehandle is not supplied, it will default to STDIN.) If there is nothing waiting in the buffer during a non-blocked read, then undef will be returned. Note that if the OS does not provide any known mechanism for non-blocking reads, then a `ReadKey -1' can die with a fatal error. This will hopefully not be common.