implementation for Parsing Expression Grammar?

In the past weeks i've been thinking over the problem on the practical
problems of regex in its matching power. For example, often it can't
be used to match anything of nested nature, even the most simple
nesting. It can't be used to match any simple grammar expressed by
BNF. Some rather very regular and simple languages such as XML, or
even url, email address, are not specified as a regex. (there exist
regex that are pages long that tried to match email address though)

I wrote out a more elaborate account of my thoughts here:
 http://xahlee.org/cmaci/notation/pattern_matching_vs_pattern_spec.html

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After days of researching this problem, looking into parsers and its
theories etc, today i found the answer!!

What i was looking for is called Parsing Expression Grammar (PEG).

See
http://en.wikipedia.org/wiki/Parsing_expression_grammar

It seems to me it's already in Perl6, and there's also a
implementation in Haskell. Is the perl6 PEG is in a usable state?

Thanks.

  Xah
  xah@[EMAIL PROTECTED]
 http://xahlee.org/

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