Regex for simply matching all words contains a certain subword in text

What is the regex for simply matching all words contains a certain subword in text( word and subword could be equal) ? I've done some searching but can't get a straight example of such a regex. This is for a program that I install so it has no bearing to any particular programming language and I can use only regex.

Example:

Word:

example

Text:

This is example. It is important that parents should set an example. examples help you to understand math.

Output words:

example, example, examples