Regular Expressions 101

^start of line

Non-Capturing Group(?:([A-Z])(?!.*?\1),?\b)+

+repeats the group contents below at least once:

Group 1([A-Z])

Character Class[A-Z]

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Negative Lookahead(?!.*?\1)

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

\1the text saved by group 1

,?optionally matches the literal , (44₁₀ / 54₈ / 2C₁₆)

\ban ASCII word boundary

$end of line

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.

26 tokens

Regular Expression

^(?:([A-Z])(?!.*?\1),?\b)+$

New

A,B
D,D,A
,B,C
B,C,
A,,B

A,B
D,D,A
,B,C
B,C,
A,,B