Regex to test if there's a word appeared exactly 2 times

Question

Given a string, test if there's a word appeared exactly two times

Input	Pass
apple banana pineapple	No
apple banana apple pineapple	Yes
apple banana banana pineapple	Yes
apple banana apple pineapple apple	No
apple banana apple banana	Yes
apple banana banana apple pineapple apple	Yes

I tried something like this but didn't work :(

^.*(\b\w+\b)(?:(?!\b\1\b).)*\b\1\b(?:(?!\b\1\b).)*$

Any suggestions? I'm using pcre.

Answer 1

Get next word. Stop if it contained exactly 2 times. Loop.

^(?*.*?\b(\w+)\b)(?>.*?\b\1\b){2}(?!.*\b\1\b)

Demo