<head>the literal text <head> (case insensitive) \s*any whitespace character, repeated any number of times
*?matches any number of characters from the set below:
\sany whitespace character
\Sany non-whitespace character
\s*any whitespace character, repeated any number of times
<the literal < (6010 / 748 / 3C16)
\/the literal / (4710 / 578 / 2F16)
head>the literal text head> (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
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters