Regular Expressions 101

Explanation
Pro

^start of line

Character Class[2-9]

2-9one character from 2 (50₁₀) to 9 (57₁₀)

Character Class[0-9]{3}

{3}matches exactly 3 characters from the set below:

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

-Wthe literal text -W (case sensitive)

Negative Lookahead(?!00)

00the literal text 00

Group 1([0-5][0-3])

Character Class[0-5]

0-5one character from 0 (48₁₀) to 5 (53₁₀)

Character Class[0-3]

0-3one character from 0 (48₁₀) to 3 (51₁₀)

Global pattern flags

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

g modifier: global. Finds all matches instead of stopping after the first

Detailed match information will be displayed here automatically.

25 tokens

^[2-9][0-9]{3}-W(?!00)([0-5][0-3])

2021-W01
2021-W02
2021-W11
2021-W20
2021-W52
2021-W53
2021-W00
2021-W99
2021-W54
2021-W54
a021-a11
2021-W111
1000-W11

2021-W01
2021-W02
2021-W11
2021-W20
2021-W52
2021-W53
2021-W00
2021-W99
2021-W54
2021-W54
a021-a11
2021-W111
1000-W11