op -- Option Pattern

        default range                   syntax
            1,$                           op[s|u]

        "op"  converts  to  or  from  UNIX  compatibility  mode.  By
        default, 'se' uses the standard subsystem  pattern  matching
        characters,  and  the  same  command characters as 'ed'.  To
        ease the transition for users familiar with the UNIX operat-
        ing system, 'se' provides a UNIX compatibility  mode.   When
        in UNIX mode, the message "UNIX" appears in the status line.

        Do  a "help se" from the shell for a complete description of
        the differences between normal operation and UNIX mode.