Regular Expressions 101

^start of line

Non-Atomic Positive Lookahead(?*.*?\b(\w+)\b)

.*?any character (except for line terminators), repeated any number of times

\ban ASCII word boundary

Group 1(\w+)

\w+any word character, repeated at least once

\ban ASCII word boundary

Atomic Group(?>.*?\b\1\b){2}

{2}repeats the group contents below exactly 2 times:

.*?any character (except for line terminators), repeated any number of times

\ban ASCII word boundary

\1the text saved by group 1

\ban ASCII word boundary

Negative Lookahead(?!.*\b\1\b)

.*any character (except for line terminators), repeated any number of times

\ban ASCII word boundary

\1the text saved by group 1

\ban ASCII word boundary

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

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

New

apple banana pineapple
apple banana apple pineapple
apple banana banana pineapple
apple banana apple pineapple apple
apple banana apple banana
apple banana banana apple pineapple apple

Regular Expression

Substitution