title: Limit a number of digits in expression
body: <p>Could you please help me write a regexp to limit humber of digits to 10 in a string (a telephone number). The problem is that we allow hyphens ("-") and spaces between the digit groups, so I can't just go with <code>/^\d{10}$/</code>.</p>
  
  <p>So the number could be 1234 123 123, or 123-123-1234 or 1234234123, with only limitation of 10 digits.</p>