Without digging deeply into the code, I think what's happening is that the data is never getting flushed.

It's probably just a matter of needing to terminate your strings with newlines:

sleep 5;
$fh = $fh[0]{'fh'};
print "send hi to child 1\n";
print $fh "shalom yeled 1\n";  # <= Note the newline to flush output

sleep 2;
$fh = $fh[1]{'fh'};
print "send hi to child 2\n";
print $fh "shalom yeled 2\n";  # <= Note the newline to flush output

sleep 2;
$fh = $fh[2]{'fh'};
print "send hi to child 3\n";
print $fh "shalom yeled 3\n";  # <= Note the newline to flush output
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