Regular Expressions 101

Pro

\ban ASCII word boundary

Branch Reset Group(?|(?=(((?:1 )+(\d?\d )\3+(?:1 )*\3+)(?:1 )*))\2|((\d?\d )\2+(?:1 )*\2+(?:1 )*))

1st Alternative(?=(((?:1 )+(\d?\d )\3+(?:1 )*\3+)(?:1 )*))\2

Positive Lookahead(?=(((?:1 )+(\d?\d )\3+(?:1 )*\3+)(?:1 )*))

Group 1(((?:1 )+(\d?\d )\3+(?:1 )*\3+)(?:1 )*)

Group 2((?:1 )+(\d?\d )\3+(?:1 )*\3+)

Non-Capturing Group(?:1 )+

+repeats the group contents below at least once:

1 the literal text 1

Group 3(\d?\d )

\d?optionally matches a digit

\da digit

the literal (32₁₀ / 40₈ / 20₁₆)

\3+the text saved by group 3, repeated at least once

Non-Capturing Group(?:1 )*

*repeats the group contents below any number of times:

1 the literal text 1

\3+the text saved by group 3, repeated at least once

Non-Capturing Group(?:1 )*

*repeats the group contents below any number of times:

1 the literal text 1

\2the text saved by group 2

2nd Alternative((\d?\d )\2+(?:1 )*\2+(?:1 )*)

Group 1((\d?\d )\2+(?:1 )*\2+(?:1 )*)

Group 2(\d?\d )

\d?optionally matches a digit

\da digit

the literal (32₁₀ / 40₈ / 20₁₆)

\2+the text saved by group 2, repeated at least once

Non-Capturing Group(?:1 )*

*repeats the group contents below any number of times:

1 the literal text 1

\2+the text saved by group 2, repeated at least once

Non-Capturing Group(?:1 )*

*repeats the group contents below any number of times:

1 the literal text 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

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25 tokens

\b(?|(?=(((?:1 )+(\d?\d )\3+(?:1 )*\3+)(?:1 )*))\2|((\d?\d )\2+(?:1 )*\2+(?:1 )*))

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