function testCurrentChar() {
                        var char = parserInput.currentChar();
                        if (typeof tok === 'string') {
                            return char === tok;
                        }
                        else {
                            return tok.test(char);
                        }
                    }
Used for custom properties, at-rules, and variables (as fallback)
Parses almost anything inside of {} [] () "" blocks
until it reaches outer-most tokens.

First, it will try to parse comments and entities to reach
the end. This is mostly like the Expression parser except no
math is allowed.