Someone needs to ping petdance (with a patch?). The documentation lies. Here's working code:

#!/usr/bin/perl
use strict;
use warnings;

use HTML::Tidy;

my $fname = join ' ', @ARGV;

my $html = do { local $/; <> }; # slurp file(s) from commandline

my $tidy = HTML::Tidy->new();

$tidy->parse( $fname, $html );

warn $_->as_string, "\n" for $tidy->messages;

print $tidy->clean( $html );
[download]

Makeshifts last the longest.