Regular Expressions 101

Pro

^start of line

Group 1(\d)

\da digit

Negative Lookahead(?!\1{3}-\1$)

\1{3}the text saved by group 1, repeated exactly 3 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\1the text saved by group 1

$end of line

\d{3}a digit, repeated exactly 3 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\da digit

$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

Detailed match information will be displayed here automatically.

27 tokens

^(\d)(?!\1{3}-\1$)\d{3}-\d$

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