^start of line
.*any character (except for line terminators), repeated any number of times
5the literal 5 (5310 / 658 / 3516)
\.the literal . (4610 / 568 / 2E16)
6the literal 6 (5410 / 668 / 3616)
$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