def marker(mark='!'):
    def deck(f):
        def wrap(*args,**kwargs):
            return f(*args,**kwargs)+mark
        return wrap
    return deck

@marker()
def doubler(s):
    return s+s

@marker(mark='%')
def tripler(s):
    return s+s+s


print(doubler('x'))

print(tripler('x'))

print(tripler('f'))

@marker(mark='^')
def tripler(s):
    return s+s+s

print(tripler('c'))