regex101: PCRE2 (PHP) Substitution Workspace

^start of line

Atomic Group(?>[^\w\n]*(\w++)(?=.*\R(\2?+[^\w\n]*\1\b)))+

+repeats the group contents below at least once:

Negated Character Class[^\w\n]*

*matches any number of characters outside the set below:

\wany word character

\na line-feed (newline) character (ASCII 10)

Group 1(\w++)

\w++any word character, repeated at least once

Positive Lookahead(?=.*\R(\2?+[^\w\n]*\1\b))

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

\Ra newline sequence

Group 2(\2?+[^\w\n]*\1\b)

\2?+optionally matches the text saved by group 2

Negated Character Class[^\w\n]*

*matches any number of characters outside the set below:

\wany word character

\na line-feed (newline) character (ASCII 10)

\1the text saved by group 1

\ban ASCII word boundary

Negated Character Class[^\w\n]*

*matches any number of characters outside the set below:

\wany word character

\na line-feed (newline) character (ASCII 10)

\Ra newline sequence

Positive Lookahead(?=\2[^\w\n]*$)

\2the text saved by group 2

Negated Character Class[^\w\n]*

*matches any number of characters outside the set below:

\wany word character

\na line-feed (newline) character (ASCII 10)

$end of line

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

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

Search reference

Regular Expression

^(?>[^\w\n]*(\w++)(?=.*\R(\2?+[^\w\n]*\1\b)))+[^\w\n]*\R(?=\2[^\w\n]*$)

New

Rough work iconoclasm but the only way to get the truth. Oliver Wendell Holmes
Rough work, iconoclasm, but the only way to get the truth. Oliver Wendell Holmes

Rule No. 1: Never lose money. Rule No. 2: Never forget rule No. 1. Warren Buffett
Rule No.1: Never lose money. Rule No.2: Never forget rule No.1. Warren Buffett

Self-esteem isn't everything, it's just that there's nothing without it. Gloria Steinem 
Self-esteem isn't everything it's just that there's nothing without it. Gloria Steinem

You said she's a senior? Babe we're all crazy.
You said, she's a senior! Babe we're ALL crazy.
You said, she's a senior? Babe we're ALL crazy!

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a a
a a a

a
a b
a b c
a b
a

Regular Expressions 101

Regular Expression

Extraction