I'll see your challenge and raise another: without looking, who can tell me the value of $_ after:

  [/.(?{$_.=$&})/g]
[download]

or how about:

  /.(?{$_.=$&})^/
[download]

Yes, this is a trick question.

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