NaiveLanguageTools

NLT is free, open-source C# lexer and GLR parser suite -- which translates to ability to parse ambiguous grammars. Grammar can be defined directly in code or (preferably) in separate file (lex/yacc-like) for included generator.

If you understand/guess the meaning of grammar in C#:

// scanning
lexer.AddStringRule(")", match => SymbolEnum.RPAREN);
// parsing
prod_builder.AddProduction(SymbolEnum.exp,
SymbolEnum.LPAREN, SymbolEnum.exp, SymbolEnum.RPAREN,
(_1, e, _3) => (AstNode)e);

or grammar in NLT format:

// scanning
/[A-Za-z_][A-Za-z_0-9]*/ -> IDENTIFIER, IdentifierSymbol.Create($text);
// parsing
program -> list:namespace_list
{ new Program(currCoords(), (Namespaces)list) };

you should be able to use it :-).

There is Example project included which serves as tutorial.