S
PL_
PL_
PL_READU{%}FROM{%},{%}{WTHEN\ELSE}
*
*      LOOP
*         READU {%1} FROM {%2} , {%3} LOCKED
*            L$$$ = YES
*         END THEN
*            L$$$ = NO
*            T$$$ = YES
*         END ELSE
*            L$$$ = NO
*            T$$$ = NO
*         END
*      WHILE L$$$ DO
*         SLEEP .1
*      REPEAT
*      IF T$$$ {%4}
      READU {%1} FROM {%2} , {%3} {%4}
