c:\@Work\Perl>perl -wMstrict -le
"print qq{perl version $]};
 ;;
 sub foo {
   my ($data) = @_;
   $$data++;
   }
 ;;
 my $x = 3;
 foo(\$x);
 print $x;
 ;;
 sub bar (\$) {
   my ($data) = @_;
   $$data++;
   }
 bar($x);
 print $x;
 ;;
 sub bof {
   $_[0]++;
   }
 bof($x);
 print $x;
"
perl version 5.008009
4
5
6