Regular Expressions 101

Positive Lookahead(?=(\b\w{4,}\b)(?:.*\b\1\b){2})

Group 1(\b\w{4,}\b)

\ban ASCII word boundary

\w{4,}any word character, repeated at least 4 times

\ban ASCII word boundary

Non-Capturing 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\w{4,}\b)(?:.*\b\1\b){3})

Group 2(\b\w{4,}\b)

\ban ASCII word boundary

\w{4,}any word character, repeated at least 4 times

\ban ASCII word boundary

Non-Capturing Group(?:.*\b\1\b){3}

{3}repeats the group contents below exactly 3 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

Global pattern flags

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

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?=(\b\w{4,}\b)(?:.*\b\1\b){2})(?!(\b\w{4,}\b)(?:.*\b\1\b){3})

hello how are you today hello hello hello

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