Regular Expressions 101

Pro

#the literal # (35₁₀ / 43₈ / 23₁₆)

\{the literal { (123₁₀ / 173₈ / 7B₁₆)

Negative Lookahead(?![.\d])

Character Class[.\d]

.the literal . (46₁₀ / 56₈ / 2E₁₆)

\da Unicode decimal digit

Positive Lookahead(?=(?<inner>(?:[\-_]{0,4}(?<![\-_]{5})[\p{L}\d]{2,}[\.\-_]?[\-_]{0,3})+))

Group inner(?<inner>(?:[\-_]{0,4}(?<![\-_]{5})[\p{L}\d]{2,}[\.\-_]?[\-_]{0,3})+)

Non-Capturing Group(?:[\-_]{0,4}(?<![\-_]{5})[\p{L}\d]{2,}[\.\-_]?[\-_]{0,3})+

+repeats the group contents below at least once:

Character Class[\-_]{0,4}

{0,4}matches between 0 and 4 characters from the set below:

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Negative Lookbehind(?<![\-_]{5})

Character Class[\-_]{5}

{5}matches exactly 5 characters from the set below:

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[\p{L}\d]{2,}

{2,}matches at least 2 characters from the set below:

\p{L}any Unicode letter

\da Unicode decimal digit

Character Class[\.\-_]?

?matches at most one character from the set below:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[\-_]{0,3}

{0,3}matches between 0 and 3 characters from the set below:

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\1the text saved by group 1

Negative Lookbehind(?<!\.)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\}the literal } (125₁₀ / 175₈ / 7D₁₆)

Global pattern flags

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

u modifier: unicode. Treats the pattern and subject as UTF-16

No unit tests · Add a test to get started

25 tokens

#\{(?![.\d])(?=(?<inner>(?:[\-_]{0,4}(?<![\-_]{5})[\p{L}\d]{2,}[\.\-_]?[\-_]{0,3})+))\1(?<!\.)\}

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