How to exclude words containing a specific string?

Question

Regular Expressions

There is such a regular expression:
/([Mm]ir[a-z]{1,3})/u
It will find 3 matches in the line: "World by world by worlds" and everything works, but in the line "World by world by worlds" it will find 4 matches, since the word "humble" fits the pattern, what should be added to it so that the word "humble" and the like do not fit the pattern?

Answer 1

Firstly, there is a case-insensitive search (flag i), and secondly, a character \bis a word boundary.