my @result =
   map
   {
       (/([a-z])$/
          ? qq{$1=>fn($2)}
          : (/([a-z])=([a-z])$/
               ? qq{$1=>$2}
               : (/([a-z])=\#([a-z])$/
                    ? qq{$1=>fn($2)}
                    : q{???}
                 )
            )
       )
   }
   split m{,}, $str;