Regular Expressions 101

Explanation
Pro

Group 1(\d)

\da Unicode decimal digit

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

{3}repeats the group contents below exactly 3 times:

\d*?a Unicode decimal digit, repeated any number of times

\1the text saved by group 1

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.

25 tokens

(\d)(?:\d*?\1){3}

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