Regular Expressions 101

(?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(?:(?:^(?:(?!hello).)*(?:\r?\n))(?=[^:]+((?(1)\1)+:\d+)))*

*repeats the group contents below any number of times:

Non-Capturing Group(?:^(?:(?!hello).)*(?:\r?\n))

^start of line

Non-Capturing Group(?:(?!hello).)*

*repeats the group contents below any number of times:

Negative Lookahead(?!hello)

hellothe literal text hello (case sensitive)

.any character (except for line terminators)

Non-Capturing Group(?:\r?\n)

\r?optionally matches a carriage return (ASCII 13)

\na line-feed (newline) character (ASCII 10)

Positive Lookahead(?=[^:]+((?(1)\1)+:\d+))

Negated Character Class[^:]+

+matches at least one character outside the set below:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

Group 1((?(1)\1)+:\d+)

Condition(?(1)\1)+

+repeats the group contents below at least once:

Uses the first branch if group 1 matched

If the condition is true, match this branch:\1

\1the text saved by group 1

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\d+a digit, repeated at least once

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

hellothe literal text hello (case sensitive)

Positive Lookahead(?=[^:]+(?:(?(1)\1)+:(\d+)))

Negated Character Class[^:]+

+matches at least one character outside the set below:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

Non-Capturing Group(?:(?(1)\1)+:(\d+))

Condition(?(1)\1)+

+repeats the group contents below at least once:

Uses the first branch if group 1 matched

If the condition is true, match this branch:\1

\1the text saved by group 1

:the literal : (58₁₀ / 72₈ / 3A₁₆)

Group 2(\d+)

\d+a digit, repeated at least once

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

(?m)(?:(?:^(?:(?!hello).)*(?:\r?\n))(?=[^:]+((?(1)\1)+:\d+)))*.*hello(?=[^:]+(?:(?(1)\1)+:(\d+)))

New

some code
more code
hey, hello!
more code

:1:2:3:4:5:6:7

Regular Expression

Substitution