Regular Expressions 101

Pro

(?m)applies the following effective flags to the remainder of the pattern: gm

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

\s+any whitespace character, repeated at least once

Positive Lookahead(?=[^()]*($[^()]*(?1)?[^()]*$)*[^()]*$)

Negated Character Class[^()]*

*matches any number of characters outside the set below:

(the literal ( (40₁₀ / 50₈ / 28₁₆)

)the literal ) (41₁₀ / 51₈ / 29₁₆)

Group 1($[^()]*(?1)?[^()]*$)*

*repeats the group contents below any number of times:

\(the literal ( (40₁₀ / 50₈ / 28₁₆)

Negated Character Class[^()]*

*matches any number of characters outside the set below:

(the literal ( (40₁₀ / 50₈ / 28₁₆)

)the literal ) (41₁₀ / 51₈ / 29₁₆)

(?1)?optionally calls group 1 as a subroutine

Negated Character Class[^()]*

*matches any number of characters outside the set below:

(the literal ( (40₁₀ / 50₈ / 28₁₆)

)the literal ) (41₁₀ / 51₈ / 29₁₆)

\)the literal ) (41₁₀ / 51₈ / 29₁₆)

Negated Character Class[^()]*

*matches any number of characters outside the set below:

(the literal ( (40₁₀ / 50₈ / 28₁₆)

)the literal ) (41₁₀ / 51₈ / 29₁₆)

$end of line

Global pattern flags

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

Detailed match information will be displayed here automatically.

25 tokens

(?m)\s+(?=[^()]*(\([^()]*(?1)?[^()]*\))*[^()]*$)

New

aa b+b   cc(dd! :(ee ((f(f g)g)) h)h) ii

aa b+b   cc(dd! :(ee ((f(f g)g)) h)h) ii