Use of reference "%s" as array index
  (W misc) You tried to use a reference as an array index; this probably
  isn't what you mean, because references in numerical context tend to be
  huge numbers, and so usually indicates programmer error.

  If you really do mean it, explicitly numify your reference, like so:
  $array[0+$ref].  This warning is not given for overloaded objects,
  either, because you can overload the numifi- cation and stringification
  operators and then you assumedly know what you are doing.

Can't call method "%s" on unblessed reference
  (F) A method call must know in what package it's supposed to run.  It
  ordinarily finds this out from the object reference you supply, but you
  didn't supply an object reference in this case.  A reference isn't an
  object reference until it has been blessed.  See per- lobj.