well, you could store your error string in a scalar and then do something like. 
foo: bar { 
    return ::processBar($item[1]); # return undef on fail
         }
   |<error: $error_string>

[download]
There's probably a more elegant way of doing this, but this was the first thing that came to mind. :)

/\/\averick

In reply to Re: RecDescent error handling by maverick
in thread RecDescent error handling by dcorbin

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