You just can't do it. Look at it from the other end, you're trying to return two lists. To assign them to two variables without using a temporary you must do a listwise assignment of the returned values. This means your code is going to look something like

  my (%baz, @bar) = foo();
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But that doesn't work with Perl, the two lists are flattened, and the first variable is in a winner-take-all situation. @bar gets nothing. At first I thought it was simply a matter of coercing on the fly

  my (%baz, @bar) = sub { %{$_[0]}, @{$_[1]} }->(foo());
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But that still doesn't work. To understand, have a look at what adding the following does:

  use Data::Dumper;
  sub foo {
    return ({J=>'A', P=>'H', }, [4.019,5.8]);
  }
  # ... original listy assignment here ...
  print Dumper(\%baz);
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There is a way around the problem of course, and that is to use references henceforth:

  my ($baz, $bar) = foo();
  print "$baz->{J} $bar->[1]\n";
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This will do what you want, at the expense of having to dereference via ->. This may or may not be a problem to retrofit into your project.