Regular Expressions 101

^start of line

foo the literal text foo (case sensitive)

Group 1([abc])

Character Class[abc]

athe literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

cthe literal c (99₁₀ / 143₈ / 63₁₆) (case sensitive)

Non-Capturing Group(?: (?!\1)((?1))(?: (?!\1|\2)(?1))?)?

?repeats the group contents below at most once:

the literal (32₁₀ / 40₈ / 20₁₆)

Negative Lookahead(?!\1)

\1the text saved by group 1

Group 2((?1))

(?1)calls group 1 as a subroutine

Non-Capturing Group(?: (?!\1|\2)(?1))?

?repeats the group contents below at most once:

the literal (32₁₀ / 40₈ / 20₁₆)

Negative Lookahead(?!\1|\2)

1st Alternative\1

\1the text saved by group 1

2nd Alternative\2

\2the text saved by group 2

(?1)calls group 1 as a subroutine

$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.

25 tokens

Regular Expression

^foo ([abc])(?: (?!\1)((?1))(?: (?!\1|\2)(?1))?)?$

New

foo a b c
foo b c a
foo a b
foo b
foo b b
foo a b 
foo a b a

foo a b c
foo b c a
foo a b
foo b
foo b b
foo a b 
foo a b a