.{3}any character (except for line terminators), repeated exactly 3 times
_the literal _ (9510 / 1378 / 5F16)
.*any character (except for line terminators), repeated any number of times
\d{3}a digit, repeated exactly 3 times
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