S
PL_
PL_
PL_READNEXT{%}FROM{%}({%}){WTHEN\ELSE}
*
      T$$$ = {%2}({%3})
      F$$$ = 1
      READNEXT {%1} FROM T$$$ ELSE
         F$$$ = 0
      END
      {%2}({%3}) = T$$$
      T$$$ = ''
      IF F$$$ {%4}
