use HTML::TreeBuilder;
my $filename = ...;
my $tree = HTML::TreeBuilder->new;
{
        open my $fileh, "<", $filename or die qq(error opening input html file "$filename": $!);
        binmode $fileh;
        my $filesize = -s $fileh;
        while (read $fileh, my $buf, (1<<16)) {
                $tree->parse($buf);
                printf(STDERR "Parsing html, %2d%%;\r", int(100*tell($fileh)/($filesize+1)));
        }
        $tree->eof;
        print STDERR "Parsing html complete.   \n";
}

##</code><code>##

use HTML::TreeBuilder;
my $filename = ...;
my $tree = HTML::TreeBuilder->new;
{
        printf STDERR "Reading html file.\n";
        open my $fileh, "<", $filename or die qq(error opening input html file "$filename": $!);
        binmode $fileh;
        local $/;
        my $filec = <$fileh>;
        eof($fileh) or die qq(error reading input html file);
        printf STDERR "Substing html file.\n";
        $filec =~ ...;
        my $filesize = length $filec;
        printf STDERR "Substed html has length %d\n", $filesize;
        my $filetell = 0;
        while (my$buf = substr $filec, 0, (1<<16), "") {
                $filetell += length $filec;
                $tree->parse($buf);
                printf STDERR "Parsing html: %2d%%;\r", int(100*$filetell/($filesize+1));
        }
        $tree->eof;
        print STDERR "Parsing html complete.   \n";
}

##</code><code>##

                $filetell += length $filec;

##</code><code>##

                $filetell += length $buf;