^start of line
Negative Lookahead(?!.*margins.*) .*any character (except for line terminators), repeated any number of times
marginsthe literal text margins (case insensitive) .*any character (except for line terminators), repeated any number of times
.*any character (except for line terminators), repeated any number of times
smargthe literal text smarg (case insensitive) .*any character (except for line terminators), repeated any number of times
$end of line
the literal ↵ (1010 / 128 / A16)
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
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters