Regular Expressions 101

Explanation

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

Non-Capturing Group(?:([a-zA-Z])(?!\1)|^)

1st Alternative([a-zA-Z])(?!\1)

Group 1([a-zA-Z])

Character Class[a-zA-Z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

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

Negative Lookahead(?!\1)

\1the text saved by group 1

2nd Alternative^

^start of line

Group 2(([a-zA-Z])\3)

Group 3([a-zA-Z])

Character Class[a-zA-Z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

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

\3the text saved by group 3

Negative Lookahead(?!\3)

\3the text saved by group 3

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)(?:([a-zA-Z])(?!\1)|^)(([a-zA-Z])\3)(?!\3)

assfdbfool 
laaate
deeeeell
tjjr
pp

$1$2$3

assfdbfool 
laaate
deeeeell
tjjr
pp