^start of line
\D*any character that's not a digit, repeated any number of times
\d{6}a digit, repeated exactly 6 times
.*any character (except for line terminators), repeated any number of 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