(?i)applies the following effective flags to the remainder of the pattern: gmi i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters
^start of line
\d+a digit, repeated at least once
\sany whitespace character
yearthe literal text year (case insensitive) s?optionally matches the literal s (11510 / 1638 / 7316) (case insensitive)
\sany whitespace character
oldthe literal text old (case insensitive) 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