Elaborating a bit on mscharrer's point, I also added use diagnostics; and ran your script. This generated the following warning:

Pseudo-hashes are deprecated at ...
    (D deprecated)  Pseudo-hashes were deprecated in Perl 5.8.0 and th
+ey
    will be removed in Perl 5.10.0, see perl58delta for more details.
    You can continue to use the fields pragma.
[download]

which pointed to your line:

foreach my $key ( keys %{$library->{place}} )
[download]

I understand that this is not the root of your problem, but it does underscore the usefulness of the warnings/strict/diagnostics pragmas in helping you to debug your code. Of course, if you are using an older version of perl, you probably would not have seen this message.