Regular Expressions 101

Pro

^start of line

Condition(?(?!(?:[^:\v]*?\.\h){3,})([^:\v]*?)\s*:\s*|)

Uses the first branch if the lookaround matches

Negative Lookahead(?!(?:[^:\v]*?\.\h){3,})

Non-Capturing Group(?:[^:\v]*?\.\h){3,}

{3,}repeats the group contents below at least 3 times:

Negated Character Class[^:\v]*?

*?matches any number of characters outside the set below:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\vany vertical whitespace character

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\hany horizontal whitespace character

If the condition is true, match this branch:([^:\v]*?)\s*:\s*

Group 1([^:\v]*?)

Negated Character Class[^:\v]*?

*?matches any number of characters outside the set below:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\vany vertical whitespace character

\s*any whitespace character, repeated any number of times

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\s*any whitespace character, repeated any number of times

Otherwise, match this branch: — matches an empty string

Group 2(.*)

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

$end of line

Global pattern flags

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

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

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25 tokens

^(?(?!(?:[^:\v]*?\.\h){3,})([^:\v]*?)\s*:\s*|)(.*)$

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