Does that work bidirectionally?

Yes, it does.

UPDATE: Sample code:

use warnings;
use strict;
use forks;
use forks::shared;
my %GLOBALHASH : shared;

share (%GLOBALHASH);

my $pid = fork ();
if (!$pid) {      # child
    $GLOBALHASH{OILPRICE} = 100;
    sleep 1;
    print "Gold price from the parent: $GLOBALHASH{GOLDPRICE}\n";
    exit 0;
} elsif ($pid)  {  # daddy
    $GLOBALHASH{GOLDPRICE} = 200;
    sleep 2;
    print "Global Oils Price is now: " . $GLOBALHASH{OILPRICE} . " dol
+lars\n";
}
[download]

Output:

Gold price from the parent: 200
Global Oils Price is now: 100 dollars
[download]