Regular Expressions 101

^start of string

Non-Capturing Group(?:\W+|(\w)(?=.*(\1\W*(?(2)\2)$)))*

*repeats the group contents below any number of times:

1st Alternative\W+

\W+any non-word character, repeated at least once

2nd Alternative(\w)(?=.*(\1\W*(?(2)\2)$))

Group 1(\w)

\wany word character

Positive Lookahead(?=.*(\1\W*(?(2)\2)$))

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

Group 2(\1\W*(?(2)\2)$)

\1the text saved by group 1

\W*any non-word character, repeated any number of times

Condition(?(2)\2)

Uses the first branch if group 2 matched

If the condition is true, match this branch:\2

\2the text saved by group 2

$end of string, or before its final line terminator

\w?optionally matches any word character

\2?optionally matches the text saved by group 2

$end of string, or before its final line terminator

Global pattern flags

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

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(?:\W+|(\w)(?=.*(\1\W*(?(2)\2)$)))*\w?\2?$

New

A man, a plan, a canal; Panama.