Assume there exists a variable myStr. Write a regular expres…

Assume there exists a variable myStr. Write a regular expression to test if the string held within myStr is exactly a non-negative number of 1 to 3 digits.  For example, 0, 1, 21, 021, and 341 should all return true, whereas -1, 1.2, abc, 1332, a21, and 21b should all return false.