Regular Expressions 101

^start of line

Positive Lookahead(?=(\d{3}\b)(.*:\r?\n)(?!\1)(\d{3})\b)

Group 1(\d{3}\b)

\d{3}a Unicode decimal digit, repeated exactly 3 times

\ba Unicode word boundary

Group 2(.*:\r?\n)

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

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\r?optionally matches a carriage return (ASCII 13)

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

Negative Lookahead(?!\1)

\1the text saved by group 1

Group 3(\d{3})

\d{3}a Unicode decimal digit, repeated exactly 3 times

\ba Unicode 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

^(?=(\d{3}\b)(.*:\r?\n)(?!\1)(\d{3})\b)

New

111 is different from:
111 is different from:
123 is different from:
567.

$0\n   *** This value $2 ***