Mostly, it's that func('&x' => 1) requires a bit too much typing, and also
makes it hard for func() to change its signature later on to accept things
other than Code.
I was discussing this with a friend of mine (Eric Livak), and he suggested
making the sigil on the name optional for disambiguation. I was wondering
if there's a possibly a way to automatically determine which parameter to
pass to based on the type of the argument. Since I'm really not that
well-versed on the language, and definitely know nothing about the
internals, I don't know if that's asking the impossible, but it seems to me
like a simple solution.