regex101: PCRE (Legacy) Match Workspace

Pro

^start of line

Character Class[a-z]

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

Positive Lookahead(?=(?:[a-z]*\d){0,4}(?![a-z]*\d))

Non-Capturing Group(?:[a-z]*\d){0,4}

{0,4}repeats the group contents below between 0 and 4 times:

Character Class[a-z]*

*matches any number of characters from the set below:

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

\da digit

Negative Lookahead(?![a-z]*\d)

Character Class[a-z]*

*matches any number of characters from the set below:

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

\da digit

Positive Lookahead(?=[a-z\d]{3,11}$)

Character Class[a-z\d]{3,11}

{3,11}matches between 3 and 11 characters from the set below:

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

\da digit

$end of line

Character Class[a-z\d]+

+matches at least one character from the set below:

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

\da digit

$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]*\d){0,4}(?![a-z]*\d))(?=[a-z\d]{3,11}$)[a-z\d]+$

New

a1a2a3a4aaaa
a3333aaaaaaa
a1a2a3aaaaa2
a1a2a3
a222
aaaa
a2aa
f2fdfgdd
w333rrrrrrr4
rrrrrrrr4444
r22rrrrrrrrr
g4fff333ffff

333333333333
1111
1aaa
1aaaaaaaaaaa
1a2aaaaaaaaa
a1aaaaaaaaaaa
a11111aaaaaa
a122a3aaaaa2
a1a2a3a4a5aa

Substitution

a1a2a3a4aaaa
a3333aaaaaaa
a1a2a3aaaaa2
a1a2a3
a222
aaaa
a2aa
f2fdfgdd
w333rrrrrrr4
rrrrrrrr4444
r22rrrrrrrrr
g4fff333ffff

333333333333
1111
1aaa
1aaaaaaaaaaa
1a2aaaaaaaaa
a1aaaaaaaaaaa
a11111aaaaaa
a122a3aaaaa2
a1a2a3a4a5aa