title: Trying to find matching regular expression
body: <p>I am trying to parse mathematical expression using regex. </p>
  
  <pre><code>Input:  2--1 
  Output: 2,-1
  </code></pre>
  
  <pre><code>Input:  2+1 
  Output: 2,1
  </code></pre>
  
  <p>Tried following but it works only for a+b scenario</p>
  
  <pre><code>Regex("[-|+]").split("2--1")
  </code></pre>