use Win32::MMF;
  
# --- in process 1 ---
my $ns1 = Win32::MMF->new( -namespace => "MyData1" );

$ns1->setvar('varid', $data);

# --- in process 2 ---
my $ns2 = Win32::MMF->new( -namespace => "MyData1" );

while (!$ns2->findvar('varid')) {};

$data = $ns2->getvar('varid');