TPIPE
if (readtoken() == TPIPE) {
} while (readtoken() == TPIPE);
if (readtoken() != TPIPE)
case TPIPE:
RETURN(TPIPE);
unlink(TPIPE);
if (mkfifo(TPIPE, 0600) == -1) {
pass = is_named_pipe(TPIPE);