my @urls = (
    "http://localhost:8080/html.htm",
);

for my $url (@urls) {
    my $html = get($url) 
        or die "Couldn't fetch page.";

    $html =~ ...
    ...
}

##</code><code>##

my @urls = (
    "http://localhost:8080/html.htm",
);

while (@urls) {
    my $url = shift(@urls);

    my $html = get($url) 
        or die "Couldn't fetch page.";

    $html =~ ...
    ...
    push @urls, $new_url;  # or @new_urls
    ...
}