Manual：Operators：Operators That Apply Functions To Results：^

everyday parser LEPL 
>>> from lepl import *
>>> (Literal('a') ^ "foo").parse('abc')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/matchers.py", line 187, in parse
    return self.null_parser(config)(stream)
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/parser.py", line 249, in single
    return next(matcher(arg))[0]
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/parser.py", line 182, in trampoline
    raise value
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/parser.py", line 165, in trampoline
    value = stack[-1].throw(value)
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/parser.py", line 91, in throw
    return self.__generator.throw(value)
  File "/usr/local/Python-3.1/lib/python3.1/site-packages/lepl/memo.py", line 113, in generator
    stream))
  File "<unknown> - use stream for better error reporting", line -1
    ...abc
lepl.error.Error: foo
>>> (Literal('a') ^ "foo").parse('bc')

なぜこの記号を？