regex101: PCRE (Legacy) Match Workspace

Pro

^start of line

Character Class[a-z]

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

Character Class[a-z0-9]*

*matches any number of characters from the set below:

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

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

Non-Capturing Group(?:_[a-z0-9]+)*

*repeats the group contents below any number of times:

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[a-z0-9]+

+matches at least one character from the set below:

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

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

Non-Capturing Group(?:(?<![0-9]),[a-z][a-z0-9]*(?:_[a-z0-9]+)*)*

*repeats the group contents below any number of times:

Negative Lookbehind(?<![0-9])

Character Class[0-9]

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

,the literal , (44₁₀ / 54₈ / 2C₁₆)

Character Class[a-z]

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

Character Class[a-z0-9]*

*matches any number of characters from the set below:

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

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

Non-Capturing Group(?:_[a-z0-9]+)*

*repeats the group contents below any number of times:

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[a-z0-9]+

+matches at least one character from the set below:

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

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

$end of line

Negative Lookbehind(?<![0-9])

Character Class[0-9]

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

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

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

25 tokens

Regular Expression

^[a-z][a-z0-9]*(?:_[a-z0-9]+)*(?:(?<![0-9]),[a-z][a-z0-9]*(?:_[a-z0-9]+)*)*$(?<![0-9])

a
abc
abc_abc
abc_d_e,abc_def
a,b,d
a12a_a
a12a_a,a12431a_a
a1_b
word1_2_word
word_2k
word_2

a,1
1,3
a,b,_
1_2
a123,aaa
a12a_a,1a

a
abc
abc_abc
abc_d_e,abc_def
a,b,d
a12a_a
a12a_a,a12431a_a
a1_b
word1_2_word
word_2k
word_2

a,1
1,3
a,b,_
1_2
a123,aaa
a12a_a,1a