I notice some problems that may or may not be connected to the issue at hand:

1. Instead of globally doing undef $/ and then manually resetting it to a newline, you can do it locally: local $/. By the way, couldn't you just set it to "0" (this is a strange input separator; does the file actually consist of null-terminated strings?)? Further reading: perlvar.
2. Use telling variable names, e.g. my ($title, $text, $exits, $things). This will save you a lot of time figuring out your own code.
3. The condition ($th eq //) is a bit odd. Don't you just want to compare with the empty string, ($th eq ""), or match with a regex denoting only whitespace, ($th =~ /^\s*$/)?
4. It seems like your input for "things" consists of a list of elements in the form "key-value-key-value-key-value". Is that right? You should perhaps show some example input.
5. Don't use barewords as keys for the hash, use strings like 'title', 'text', 'exit', 'things'.
6. You seem to intend to create a hash reference for 'things'. This is done with a backslash: ... 'things' => \%things ....
7. You should close your filehandle when done.
8. Instead of returning from the function lookat inside the if statement, the clear way of conveying your meaning is to use an else clause.