1the literal 1 (4910 / 618 / 3116)
\s+any whitespace character, repeated at least once
1-9one character from 1 (4910) to 9 (5710)
\d*a digit, repeated any number of times
$end of line
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