Implementing Kleene star operator * (sort of) in C program

Question

For any user input string A ,with at least one instance of the star operator *,verify that input string B can be produced by A. For example: go*s can produce the strings goes,goners,goals etc. I can't figure out a way to implement this. I thought i could compile some specific regex for each user input word like: /(substring1)[a-z]*(substring2)/ but it turned out really difficult to dynamically create the expression for every possible user input(given the scope of this exercise being basic string manipulation). In the case of "gossss" how can i make sure that the 1st "s" is part of the * and not the final "s" in the word go*s? Any thoughts on this?