Regular Expressions 101

^start of string

Non-Capturing Group(?:[^a-z]*([a-z])(?=.*(\1[^a-z]*\2?+)$))+

+repeats the group contents below at least once:

Negated Character Class[^a-z]*

*matches any number of characters outside the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Group 1([a-z])

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Positive Lookahead(?=.*(\1[^a-z]*\2?+)$)

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

Group 2(\1[^a-z]*\2?+)

\1the text saved by group 1

Negated Character Class[^a-z]*

*matches any number of characters outside the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\2?+optionally matches the text saved by group 2

$end of string, or before its final line terminator

Negated Character Class[^a-z]*

*matches any number of characters outside the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Character Class[a-z]?

?matches at most one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Negated Character Class[^a-z]*

*matches any number of characters outside the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\2the text saved by group 2

$end of string, or before its final line terminator

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

^(?:[^a-z]*([a-z])(?=.*(\1[^a-z]*\2?+)$))+[^a-z]*[a-z]?[^a-z]*\2$

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