How to add zero in front of single digit values using REGEX in pentaho

I have the month values in a flat file like

Month
  12
  11
   1
   2
   8
  10

now i want to add zero in front of single digit values & double digit as same.

output should be like

Month
  12
  11
  01
  02
  08
  10

This am doing in PENTAHO (I will implement in Replace in string step)

I am not aware of PENTAHO. But following regex should work for most of the languages

Match : \b([1-9])\b

Replace : 0$1

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