Regular Expressions 101

^start of string

Group 1((.+)(?:.*))

Group 2(.+)

.+any character (except for line terminators), repeated at least once

Non-Capturing Group(?:.*)

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

\1+the text saved by group 1, repeated at least once

\2?optionally matches the text saved by group 2

$end of string, or before its final line terminator

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Regular Expression

^((.+)(?:.*))\1+\2?$

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