c:\@Work\Perl>perl -wMstrict -MData::Dumper -le
"my $hash = {};
 print 'Ma: ', $hash;
 ;;
 do_something($hash);
 ;;
 print 'Mb: ', $hash;
 print Dumper($hash);
 ;;
 sub do_something {
   print 'Sa: ', $_[0];
   ;;
   $_[0] = { a => 'alpha',  b => 'beta', };
   print 'Sb: ', $_[0];
   print Dumper( $_[0] );
   }
"
Ma: HASH(0x92d06c)
Sa: HASH(0x92d06c)
Sb: HASH(0x92d16c)
$VAR1 = {
          'a' => 'alpha',
          'b' => 'beta'
        };

Mb: HASH(0x92d16c)
$VAR1 = {
          'a' => 'alpha',
          'b' => 'beta'
        };