- Work directory.
     You can use (::) as path name of the work directory.
     ex). ::xyz   --->file name xyz in the work directory.
     Especially ::cb is work file used for Cut and Paste,
     You can also edit it directly, then paste it.
     ::so is stdout+stderr from OS native command to chk result of command.
     After write into work directory by REPl ::tmp,
     read it into current screen     by COPy ::tmp.
     It is alternative way of Cut & Paste.
     By APPend cmd you can gather copy source line from files.
#ifdef UNX
     You must specify work directory by env-variable(export xe=xxx)
     or by command line parameter(-wxxx).
     Work directory named xe_wdnnnnn(nnnnn:user id) is created
     automatically in ~/ (HOME) if none is specified.
#else
     You must specify work directory by environment variable(set xe=xxx)
     or by command line parameter(/Wxxx).
     If none is specified, c:\xe_wd is created and used as work dir.
#endif