Regular Expressions 101

<the literal < (60₁₀ / 74₈ / 3C₁₆)

Group 1(LastName)

LastNamethe literal text LastName (case sensitive)

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Group 2(.*?)

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

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\1the text saved by group 1

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Negative Lookahead(?![\s\S]*?<\1>\2<\/\1>)

Character Class[\s\S]*?

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

\sany whitespace character

\Sany non-whitespace character

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\1the text saved by group 1

>the literal > (62₁₀ / 76₈ / 3E₁₆)

\2the text saved by group 2

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\1the text saved by group 1

>the literal > (62₁₀ / 76₈ / 3E₁₆)

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.

Search reference

Regular Expression

<(LastName)>(.*?)<\/\1>(?![\s\S]*?<\1>\2<\/\1>)

New

                  <LastName>Adams</LastName>
                  <LastName>Adams</LastName>
                  <LastName>Yellow</LastName>
                  <LastName>Adams</LastName>