I really enjoyed this golf - there are so many unique approaches one could take. Here's one at 78:

sub is_fibo {
  push@_,length$&while$_[0]=~/^|(.)\1*/g;{@_>3?pop==$_[-1]+$_[-2]?redo
+:0:pop==1}
}
[download]

   MeowChow                                   
               s aamecha.s a..a\u$&owag.print