This seems to work:

sub fubar {
     my $ref = shift;
     ${$ref} = 4;
     print "$$ref\n";
  }
[download]

and I'm assuming you're using ref's to scalars as a learning experience. I dunno if the $$_&lbr;0] (sorry, forgot the code for left bracket) is putting another layer of ref in there. Likewise:

feebar(\$blahblah);
sub feebar {
   my $ref = shift;
   $$ref = 4;
   print "$$ref\n";
}
[download]

works too. More questions? Buy Object Oriented Perl (by D. Conway) As good a 30 bucks as you can spend on perl manuals (not the best, but as good as ... ;-).

a