I had my $html="htmlfilepath"; added to your code.
Running your code is giving the below error,
Use of uninitialized value in subroutine entry at C:/Perl/site/lib/HTML/TreeBuil
der.pm line 121.
Re^2: Parsing HTML files
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If you would have taken the time to read the documentatio, e.g. using "perldoc HTML::TreeBuilder", you should have seen, if the method name parse_content wasn't obvious enough already, that to parse a file, you should use the parse_file method.