What about Access and Printing of a HASH OF HASHES?

Simply create a 2-level loop and iterate through the keys of each level.

# untested:
my @urls;
for my $outer ( keys %hash ) {
  for my $inner ( keys %{ $hash{$outer} } ) {
    # maybe check before, if entry "url" exists or is defined ...
    push @urls, $hash{$outer}->{$inner}->{url};
  }
}
[download]

update:

I missed last night that there is an anonymous array inside $hash{$outer}->{$inner}; so here's an updated code:

for my $outer ( keys %hash ) {
    for my $inner ( keys %{ $hash{$outer} } ) {
        push @urls, map { $_->{url} }  @{ $hash{$outer}->{$inner} }
    }
}
[download]

As the other answers point out, if there is only one "outer" and one "inner" key, you can skip the loops and access the inner referenced array directly...