Fix scalar quoting when starts with non-ASCII character

Pattern `\W` matches also non-ASCII letters in Ruby (see [docs](http://www.ruby-doc.org/core-2.1.2/Regexp.html#class-Regexp-label-Metacharacters+and+Escapes)), thus `[^[:word:]]` should be used instead. It works exactly like `\W`, but also for non-ASCII characters.