function _createSpecialLineExp(lineSyntax, blockSyntax) {
        var i, character, escapedCharacter,
            subExps   = [],
            prevChars = "";

        for (i = lineSyntax.length; i < blockSyntax.length; i++) {
            character = blockSyntax.charAt(i);
            escapedCharacter = StringUtils.regexEscape(character);
            subExps.push(prevChars + "[^" + escapedCharacter + "]");
            if (prevChars) {
                subExps.push(prevChars + "$");
            }
            prevChars += escapedCharacter;
        }
        return new RegExp("^\\s*" + StringUtils.regexEscape(lineSyntax) + "($|" + subExps.join("|") + ")");
    }
@private
Creates special regular expressions that matches the line prefix but not the block prefix or suffix
@param {!string} lineSyntax  a line comment prefix
@param {!string} blockSyntax  a block comment prefix or suffix
@return {RegExp}