regex101: Camel Case - no digits allowed - Upto 3 upper case letters

Pro

^start of line

Character Class[a-z]

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

Character Class[a-z]*

*matches any number of characters from the set below:

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

Group 1(([A-Z]{1,3}[a-z]+)*[A-Z]{0,3}|([a-z]+[A-Z]{1,3})*|[A-Z]{1,3})

1st Alternative([A-Z]{1,3}[a-z]+)*[A-Z]{0,3}

Group 2([A-Z]{1,3}[a-z]+)*

*repeats the group contents below any number of times:

Character Class[A-Z]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[a-z]+

+matches at least one character from the set below:

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

Character Class[A-Z]{0,3}

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

2nd Alternative([a-z]+[A-Z]{1,3})*

Group 3([a-z]+[A-Z]{1,3})*

*repeats the group contents below any number of times:

Character Class[a-z]+

+matches at least one character from the set below:

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

Character Class[A-Z]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

3rd Alternative[A-Z]{1,3}

Character Class[A-Z]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

$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

25 tokens

Regular Expression

^[a-z][a-z]*(([A-Z]{1,3}[a-z]+)*[A-Z]{0,3}|([a-z]+[A-Z]{1,3})*|[A-Z]{1,3})$

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