Regular Expressions 101

^start of line

Negative Lookahead(?!,)

,the literal , (44₁₀ / 54₈ / 2C₁₆)

Negative Lookahead(?!.*,,)

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

,,the literal text ,,

Negative Lookahead(?!.*(\b[A-Z]+\b).*\1)

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

Group 1(\b[A-Z]+\b)

\ban ASCII word boundary

Character Class[A-Z]+

+matches at least one character from the set below:

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

\ban ASCII word boundary

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

\1the text saved by group 1

Character Class[A-Z,]+

+matches at least one character from the set below:

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

,the literal , (44₁₀ / 54₈ / 2C₁₆)

Negative Lookbehind(?<!,)

,the literal , (44₁₀ / 54₈ / 2C₁₆)

$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

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

New

A,B
A,B,C,D,E,F
D,D,A
,B,C
B,C,
A,,B,C

A,B
A,B,C,D,E,F
D,D,A
,B,C
B,C,
A,,B,C