Function Signatures: Return Types (replace wantarray?)

[Tom Browder]

I need to replace the Perl 5 'wantarray' and think a multi method with
differing return types should do it.

So I've tried this:

multi method foo($a, $b --> {Num,Num}) { #... }
multi method foo($a, $b --> Num) { #... }

and get errors like:

Missing block
at Ellipsoid.pm:672
------> ethod to($lat1, $lon1, $lat2, $lon2 --> �{Rat, Rat})
  from test_ellipsoid.pl:12

I've tried parentheses, square brackets, and no grouping characters
instead of curly braces but that doesn't change the error.

Question:

How does one properly provide differing function return type signatures?

Thanks.

Best,

-Tom