Erm, from the m// right above it. Read perldoc perlop and perldoc perlretut.

Update: And not entirely related but to paraphrase von Neuman, "Those attempting to parse HTML with regular expressions are living in a state of sin.". HTML::TreeBuilder or HTML::TokeParser or the like are much better. The regex will work in this case, but in general it's better to use a real parser.