You're either not showing us all the relevant code, or you have subtly changed it as you've entered it here, because what you;ve posted works as expected:

use Data::Dumper;

sub mylog{ print @_ }

my %shared_data = (
'dtLastRcvMsg' => time,
'dummy2' => 33,
'dummy' => 5
);

my $p1 = \%shared_data;
mylog( "P1: ($p1) " . Dumper( $p1 ));

$self->{'shared_data'} = $p1;

my $p2 = $self->{'shared_data'};
mylog( "P2: ($p2)" . Dumper( $p2 ));

__END__
c:\test\691728>..\junk.pl
P1: (HASH(0x18245bc)) $VAR1 = {
          'dummy2' => 33,
          'dummy' => 5,
          'dtLastRcvMsg' => 1213694057
        };
P2: (HASH(0x18245bc))$VAR1 = {
          'dummy2' => 33,
          'dummy' => 5,
          'dtLastRcvMsg' => 1213694057
        };
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