title: Regex in R: Return index of the last digit of the first instance of numeric characters in a string
body: <p>Following are sample outputs</p>
  
  <pre><code>Input_String                |   output_col1   |   output_col2
  a-123/123 Lion's park       |   a-123/123     |   Lion's park
  b/11-341 lion 34 park       |   b/11-341      |   lion 34 park
  flat 701 sector 4 city x    |   flat 701      |   sector 4 city x
  </code></pre>
  
  <p>if the numbers are separated by alphabets, they need to be considered as different numbers and only the first incidence needs to be captured in <code>output_col1</code>, and if they are separated by punctuations they should be considered as one single number.</p>