A bit more clearly: 
my $pages = $data->{query}{pages};
my ($page_id) = keys(%$pages);
my $page = $pages->{$page_id};
my $extract = $page->{extract};
...

[download]

Or if you don't need the page id: 

my $pages = $data->{query}{pages};
my ($page) = values(%$pages);
my $extract = $page->{extract};
...

[download]

The layout suggests that multiple pages could be returned. 

my $pages = $data->{query}{pages};
for my $page_id (keys(%$pages)) {
   my $page = $pages->{$page_id};
   my $extract = $page->{extract};
   ...
}

[download]

Or if you don't need the page id: 

my $pages = $data->{query}{pages};
for my $page (values(%$pages)) {
   my $extract = $page->{extract};
   ...
}

[download]

In reply to Re^2: hash of hashes parsing problem by ikegami
in thread hash of hashes parsing problem by Takamoto

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