PROGRAM Example6 IS

    INSTRUCTION TurnBackAndInfect IS
        TurnBack
        TryToInfect
    END TurnBackAndInfect

    INSTRUCTION TryToInfect IS
        IF next-is-enemy THEN
            infect
        END IF
    END TryToInfect

    INSTRUCTION TurnBack IS
        turnright
        turnright
    END TurnBack

    INSTRUCTION AdvanceIfPossible IS
        IF next-is-empty THEN
            move
        ELSE
            TryToInfect
            TurnBackAndInfect
        END IF
    END AdvanceIfPossible

BEGIN
    WHILE true DO
        AdvanceIfPossible
    END WHILE
END Example6