regex: match nested HTML tags

gistfile1.txt

# This will capture the contents of the div of interest, including any nested div tags.
use 5.010;
my ($div) = $content =~ m[
    \Q<div id="matchme">\E
    ( (?> [^<]++ | <(?!/?div\b) | <div\b[^>]*+>(?1)</div> )*+ )
    </div>
]x;