What you've described is exactly what I'm trying to figure out how to do. The question is how do I test that the connection has either succeeded or failed? I tried this, since the Net::OpenSSH documentation says that a failure returns undef or an empty list:

 $ssh{$host} = Net::OpenSSH->new($host, master_opts => [-i => "/path/t
+o/key"]);
    if(defined $ssh{$host}) {
      print STDOUT "SSHD is back up. Continuing...\n";
    }
    else {
      print STDOUT "Still waiting for SSH. Retrying in 5 seconds...\n"
+;
      sleep 5;
    }
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This fails though. Apparently the "no route to host" message that comes back from the failed connection attempt is enough to define $ssh{$host}. What's a good way to test to see if the connection is successful?

Use the error method to see if some error happened.

for my $host (...) {
    $ssh{$host} = Net::OpenSSH->new($host, ...);
    if($ssh{$host}->error) {
        print STDOUT "Still waiting for SSH. Retrying in 5 seconds...\
+n";
        sleep 5;
        redo;
    }
    else {
        print STDOUT "SSHD is back up. Continuing...\n";
    }
}
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If you are starting several connections in parallel, you can also use the wait_for_master method.

That worked! Thanks for the reply (and the great module).

Passing in parameters works for me, without having to loop & check the error condition:

my $ssh = Net::OpenSSH->new( $username . "\@" . $host, 
                             key_path => $key_path,
                             master_opts => [-o => "ConnectionAttempts
+=30", -o => "ConnectTimeout=10"] );
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