Smells like a job for HTML::Treebuilder! Which in turn uses HTML::Parser, which in turn uses HTML::Element, which in turn provides you with the ridiculously powerfull look_down method... Assuming $content contains the page you got back;

use HTML::TreeBuilder;
my $tree = HTML::TreeBuilder->new;
$tree->parse($content);
$tree->eof;
my @hidden_field_elements = $tree->look_down(
    _tag => "input",
    type => "hidden",
);
my %hidden_fields = 
    map { $_->attr('name') => $_attr('value') }
        @hidden_field_elements;
[download]

This might work as it is, or it may have some typos in there. You get the <IMG> tag though... Uh... picture.

I must recommend that you not use this method though, because it makes solving this challenge so easy it can only be considered cheating. And you don't wanna be a cheat right?

The man-pages for HTML::Element, ::Parser and ::TreeBuilder are also criminally complete and can easily be used to convince any PHP'r that he's barking up the wrong (pear)tree.

Happy coding!