No, I don't know what the original data was, but it would mean something like this:

If we have this variable:

   my $a = [ 
      { 
        foo => { 
            foo2 => {
                 foo3 => 'xxxx'
            }
        },
        bar => {
            bar2 => {
                 bar3 => 'yyyy'
            }
        }
      },
      {
        FOO => { 
            FOO2 => {
                 FOO3 => 'xxxx'
            }
        },
        BAR => {
            BAR2 => {
                 BAR3 => 'yyyy'
            }
        }
       },
   ];
[download]

And we assign variable $b to point to part of it, and then we undef the original:

   my $b = $a->[1]{BAR};
   undef $a;
[download]

Then only the references referred to by $b continue to exist:

   use Data::Dumper;
   print Dumper ($a,$b);
   > $VAR1 = undef;
     $VAR2 = {
          'BAR2' => {
                     'BAR3' => 'yyyy'
                    }
           };
[download]

Clint