Requesting some RegEx help! Modifying Textile behavior.

gistfile1.txt

This regex:
$this->urlch = '[\w"$\-_.+!*\'(),";\/?:@=&%#{}|\\^~\[\]`]';

As part of this in PHP:

return preg_replace_callback('/
            (?:^|(?<=[\s>.$pnct\(])|([{[])) # $pre
            "                            # start
            (' . $this->c . ')           # $atts
            ([^("|\]]+)                      # $text
            \s?
            (?:\(([^)]+)\)(?="))?        # $title
            ":
            ('.$this->urlch.'+)          # $url
            (\/)?                        # $slash
            ([^\w\/;]*)                  # $post
            (?:([\]}])|(?=\s|$|\)))
        /Ux', array(&$this, "fLink"), $text);

Is responsible for parsing out links in Textile if I'm correct.

Normal behavior of textile knows links like this:

"This is a link":http://www.google.com

Now I need to change that to allow a MODX implementation, where in links are generated dynamically by replacing "tags". Something like this needs to work, next to the regular behavior.

"This is a dynamic link":[[~245]]

I've been trying to figure it out but failed so far. I know basic RegEx, but this is way too complex for what I can handle, lol. Any help appreciated..