add use diagnostics; to get better error messages; you asked for the free help of strict and warnings but you're not Coping with Scoping yet, see these links and my

I've read a lot about iterating on hashes and arrays, but I'm blocked by the complexity of the JSON. Why it tells me about %oneservice if I declared it as $oneservice?

Because you skipped reading perlintro. Because  %foo is accessed as  $foo{bar} but $baz is accessed as  $baz->{bar}. See also References quick reference