Parsing complex structured text data?

If there is already a specialised parser for your particular data, use that - that is, don't create another XML parser!

For the special case of Windows .INI files and Unix configuration files, consider the Penlight pl.config module.

Lua is strong at text processing - you can use the built-in string patterns, PCRE regular expressions, or Lpeg.

Sometimes a lexical scanner gives a cleaner solution than pattern matching. This works particularly well if your 'complex structured text' is Lua or C code.