Regular Expressions 101

Positive Lookahead(?=((?:A\d+\s+)+B\.))

Group 1((?:A\d+\s+)+B\.)

Non-Capturing Group(?:A\d+\s+)+

+repeats the group contents below at least once:

Athe literal A (65₁₀ / 101₈ / 41₁₆) (case sensitive)

\d+a Unicode decimal digit, repeated at least once

\s+a Unicode whitespace character, repeated at least once

Bthe literal B (66₁₀ / 102₈ / 42₁₆) (case sensitive)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

(?=((?:A\d+\s+)+B\.))

New

A2 A1 B.
A1 B.
A3 A1 A8 B.