Code
regex
[abc] any of a, b, c
[^abc] none of a, b, c
[a-z] range a to z
[A-Z0-9] uppercase letter or digit
\d digit [0-9]
\D non-digit
\w word char [A-Za-z0-9_]
\W non-word char
\s whitespace
\S non-whitespace
. any char except newline