c:\@Work\Perl\monks>perl -wMstrict -MData::Dumper -le
"my %fields;
 %fields = (
   version1    => { 1 => 'Ok' },
   version_TWO => $fields{version1},
   );
 print Dumper \%fields;
 ;;
 $fields{version1}{1} = 'Oops...';
 ;;
 print $fields{version_TWO}{1};
"
$VAR1 = {
          'version_TWO' => undef,
          'version1' => {
                          '1' => 'Ok'
                        }
        };

Use of uninitialized value in print at -e line 1.