class T(str):

    def __matmul__(self, xs):
        return self[::-1] + xs[::-1]

    def __rmatmul__(self, xs):
        return xs[::-1] + self[::-1]

    def __imatmul__(self, xs):
        return self[::-1] + xs[::-1]


xs = T('ahoj')
ys = T('123')

# __matmul__
print(xs @ ys)      # 'joha321'
print(xs @ 'ABC')   # 'johaCBA'

# __rmatmul__
print('ABC' @ xs)   
# bez __rmatmul__:
#   TypeError: unsupported operand type(s) for @: 'str' and 'T'
# s __rmatmul__:
#   'CBAjoha'

# __imatmul__
zs = T('!?')
zs @= ys
print(zs)           # '?!321'