title: Reg-Exp for 0,0.0 or 100.20 or 0.99 or 9999.99
body: <p>I want to be able to allow 0 or 0.0 or 100.20 or 1000 or 0.99</p>
  
  <p>I want to enter 4 digit+decimal point+2 digit</p>
  
  <p>Where decimal &amp; 2 digit are not mandatory &amp; out of 4 digits I want to allow 1 digit too</p>
  
  <p>I want the exact regex to match this.</p>