My favourite module for parsing HTML is HTML::TreeBuilder::XPath, but it misses out on the first div (id=Zero). It uses HTML::Parser internally but I could not find a way to pass the necessary attribute empty_element_tags=>1 from HTML::TreeBuilder to HTML::Parser.

So here is a fairly verbose version using just HTML::Parser:

use HTML::Parser;

my $file = 'example.html';
my ($in_div,$in_wanted_div) = (0,0);
my @result;

my $parser = HTML::Parser->new(
    api_version => 3,
    start_h => [\&start, "tagname, attr"],
    text_h => [\&text, "dtext"],
    end_h => [\&end, "tagname"],
    empty_element_tags => 1,
);
$parser->parse_file($file);

print join(', ',@result);

sub start {
    my ($tag, $attr) = @_;
    return unless ($tag eq 'div');
    if (exists $attr->{'class'} and $attr->{'class'} eq 'data') {
        $in_div = 1;
        $in_wanted_div = 1;
        push(@result, "$attr->{'id'}=");
    }
    else {
        $in_div++;
    }
}

sub text {
    my ($text) = @_;
    return unless $in_wanted_div;
    $text =~ s/\W//g;
    $result[-1] .= $text;
}

sub end {
    my ($tag) = @_;
    return unless ($tag eq 'div');
    $in_div--;
    $in_wanted_div = 0 if not $in_div;
}
[download]

Output:

Zero=, One=Monday, Two=Tuesday, Three=Wednesday, Four=Thursday, Five=F
+riday, Six=Saturday, Seven=Sunday
[download]