So, "%" would be nice, but "freaking awesome"?? ... I dunno. Between variable interpolation and sprintf (or Interpolation if you really want to get fancy), you get nearly the same functionality in perl, and I don't think I would miss python's "%" much (if I missed it at all, which I don't, because I don't use python).
And originally, I wasn't even talking about "%" in perl. It's freaking awesome in Vim though :-)