Regular Expressions 101

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?:(?<!\b[0-9]{4}-)|(?![0-9]{2}(?:[0-9]{2})?\b))

1st Alternative(?<!\b[0-9]{4}-)

Negative Lookbehind(?<!\b[0-9]{4}-)

\ba Unicode word boundary

Character Class[0-9]{4}

{4}matches exactly 4 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

2nd Alternative(?![0-9]{2}(?:[0-9]{2})?\b)

Negative Lookahead(?![0-9]{2}(?:[0-9]{2})?\b)

Character Class[0-9]{2}

{2}matches exactly 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Non-Capturing Group(?:[0-9]{2})?

?repeats the group contents below at most once:

Character Class[0-9]{2}

{2}matches exactly 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

\ba Unicode word boundary

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

-(?:(?<!\b[0-9]{4}-)|(?![0-9]{2}(?:[0-9]{2})?\b))

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Studied b-tech from college in 2010-13

Studied b-tech from college in 2010-2013

Studied b-tech from college in 2010-13 at B-college