A tasking CALL statement is not allowed from a PUT FILE (SYSPRINT) statement because no programs in the attempted new task via the tasking CALL statement can produce output on SYSPRINT while a PUT statement is running, and task interlock is likely to occur.

DCL X FIXED BIN(15);
PUT LIST(F(X));
F:  PROC(X);
CALL E TASK;
X=5;
RETURN (X);
END F;
E:  PROC;
END E;