Regular Expressions 101

Definition Group(?(DEFINE)(?'pat'a|ab))

Group pat(?'pat'a|ab)

1st Alternativea

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

2nd Alternativeab

abthe literal text ab (case sensitive)

^start of string

(?P>pat)calls group pat as a subroutine

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

$end of string, or before its final line terminator

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?(DEFINE)(?'pat'a|ab))^(?P>pat)b$

New

ab