in reply to Why do you need to escape a string used as a paramater?
The "\" in this case makes a reference to the variable $intr_html. When a "normal" variable is given to HTML::TokeParser::new, it is taken to be a filename to open and read. When a reference is given, it is taken to be a "pointer" to the text in $intr_html to be parsed.
See perlreftut for a tutorial on references and perlref for all the details.
Arjen
In Section
Seekers of Perl Wisdom